The Hyperscanning of 'Paranormal Activity': A Neurocinematic Study of Collective Fear

Still from the promotional trailer for that viral movie phenomenon, Paranormal Activity.

Not since The Blair Witch Project (1999)¹ ten years ago (in the BT [Before Twitter] dark ages) has there been such a grassroots "underground" buzz surrounding a cult-like, deliberately amateur, mega-scary, "found" reality footage-type movie. Unlike its predecessor, Paranormal Activity does get to benefit from Twitter as a trending topic:

Paranormal Activity is a popular topic on Twitter right now.

A ultra low-budget horror film about a couple experiencing demonic forces at night. The US limited release was Sept. 29, 2009, and there will supposedly be a nationwide release if it gets a million votes on Eventful.

51 more tweets since you started searching.



Here's the trailer:



Beyond word-of-mouth from the original target demographic attending midnight shows in college towns, mainstream media outlets such as CNN have picked up on the buzz:

Surprise hit 'Paranormal Activity' scares money out of moviegoers

updated 8:01 p.m. EDT, Mon October 12, 2009

(CNN) -- The new horror movie "Paranormal Activity" could be filling movie studio marketing departments with fear.

Using a campaign of limited showings, social media and word-of-mouth fan buzz, the film has managed to become a breakout hit without the aid of a glitzy marketing campaign -- or even a traditional movie trailer.

According to Variety, the very low-budget film (it reportedly cost $11,000), which played in fewer than 200 theaters, raked in $7.1 million over the weekend -- a record for a limited-release film. The film had an impressive $44,163 per-screen average and placement in the top five of the box office ratings over the weekend.

Most relevant for the ongoing Neurocinema Collection™ is this observation:

"Watching it with 250 strangers in a movie theater and getting everybody to jump at the same time definitely has an effect," [Kevin Carr] said. "It's the event film right now of the year, which is something that needs to be experienced."

"Watching it with 250 strangers in a movie theater" is the key phrase. We'll return to that later.

In the last post we learned about the new interdisciplinary field of “neurocinematic” studies. The term first appeared² in the scholarly journal Projections: The Journal for Movies and Mind, in a 2008 paper written by Hasson and colleagues:

This article describes a new method for assessing the effect of a given film on viewers’ brain activity. Brain activity was measured using fMRI during free viewing of films, and inter-subject correlation analysis (ISC) was used to assess similarities in the spatiotemporal responses across viewers’ brains during movie watching. Our results demonstrate that some films can exert considerable control over brain activity and eye movements. However, this was not the case for all types of motion picture sequences, and the level of control over viewers’ brain activity differed as a function of movie content, editing, and directing style. We propose that ISC may be useful to film studies by providing a quantitative neuroscientific assessment of the impact of different styles of filmmaking on viewers’ brains, and a valuable method for the film industry to better assess its products.

The NYU researchers, led by Uri Hasson (now at Princeton), claim to study "to what extent are we all alike?"³ The research program originated in the laboratory of Prof. Rafael Malach and first hit the Science scene in 2004. In that study, five participants watched the first 30 min of The Good, The Bad, and The Ugly in an MRI scanner. The data were analyzed to determine commonalities in brain activation across subjects, revealing that 25% of the cortex showed significant intersubject correlation during the movie. The Projections article summarizes the results from subsequent experiments and develops the idea that different directors, and different filmmaking styles, exert varying levels of "control" over audio-visuo-higher-level cortical responses in the brains of the viewers.

This is all very interesting, you say, but it doesn't mimic the real life movie-going experience. How can you possibly evaluate the neural effects of watching a scary movie in a theater with 250 strangers?

The Hyperscanning of 'Paranormal Activity': A Neurocinematic Study of Collective Fear

In this imaginary experiment,⁴ the viewing experience is enhanced through several means. While in laying supine in the MRI scanner, individual research participants watch a specially-made DVD of Paranormal Activity shot from the perspective of the audience, as in the trailer. To encouraging bonding among the research subjects, the cool "hyperscanning" methodology is used. This technique was developed by Read Montague and his co-workers (Montague et al., 2002). Typically, hyperscanning involves two subjects who interact with each other while their brains are scanned simultaneously (in adjoining or distant magnets). Specially developed software (Networked Experiment Management Objects, or NEMO) coordinates the experiments across sites:

The scarcity of neuroimaging resources limits the ability to perform multi-subject experiments within the same facility, necessitating the ability to simultaneously scan across multiple institutions. Furthermore, in order to correlate behavior and brain activation among participants, sites participating in Hyperscan experiments must be synchronized so that the behavioral and imaging data gathered during the experiment can be reconciled to a common timeline.

Professional software developers at the Human Neuroimaging Laboratory (HNL) have created a distributed framework for executing Hyperscan experiments. The framework, called NEMO, consists of client and server components written in Java, a SQL database for storing experiment metadata and results, an experiment script execution environment based on the Jython scripting language, and pulse-sequence customizations to facilitate network-initiated scanning.

For our fright-filled neurocinematic study, five friends are scanned simultaneously. Each subject is informed that he/she will be watching the movie at the exact same time as the others, experiencing the exact same scanner environment (which can be claustrophobic, even under calm conditions). They're instructed that they must be still. They're asked to view the movie as a shared experience -- shared with the audience and with their friends. In an alternate scenario, ten strangers can meet each other beforehand through video conferencing and follow the same procedures. In either case, the data are analyzed for intersubject correlations not only in the cortex, but also in subcortical regions important for emotion (amygdala) and memory (hippocampus).

What percentage of brain activity will be correlated across subjects? Hasson et al. (2008) discussed the continuum of control employed by filmmakers: real life --> documentaries --> art films --> Hollywood --> propaganda. The filmmaking style of PA is not at all sophisticated in the vein of Alfred Hitchcock Presents, which

evoked similar responses across all viewers in over 65 percent of the cortex, indicating a high level of control of this particular episode on viewers’ minds.

Nevertheless, despite using shaky-cam real life amateurish filmmaking with little editing, the viewers' attention is directed to restricted locations: the bed, the door, the hallway, Katie Featherston's breasts [just out of frame, but there are a lot of deliberate close-ups], her face. These would activate category-specific regions in the visual processing stream: the parahippocampal place area, the fusiform face area, the extrastriate body area. Importantly, emotional reactions might be similar among like-minded friends, adding a new dimension to the ISC data.

But will the study provide a privileged (neural) measure of collective fright, beyond what can be revealed by eye movements and by peripheral autonomic responses such as heart rate and skin conductance? I don't know, but it'll sure make for great articles in Wired and CNN. And Science. Be sure to mention me in the Acknowledgments.



What is my opinion of Paranormal Activity? I went to the late show tonight, and I have to say...... the movie is WAY overrated.⁵ I didn't find it scary at all. You're waiting so long for something to happen, that a slight noise or movement of the door or a brief shadow are supposed to be scary. I kept waiting to jump out of my seat but never did, not even in the last 30 seconds. The trailer for Shutter Island was more frightening.

Footnotes

¹ I thought BWP was highly overrated and not scary at all.

² Correct me if I'm wrong.

³ From a neuroscientific standpoint, certain aspects of these findings can be considered trivial, as noted by an anonymous commenter. For this post, I have adopted a willing suspension of disbelief for artistic purposes.

⁴ For an earlier post about another fake experiment, see The Neurology of Twitter:

It was bound to happen. Some neuroimaging lab will conduct an actual fMRI experiment to examine the so-called "Neural Correlates of Twitter" -- so why not write a preemptive blog post to report on the predicted results from such a study, before anyone can publish the actual findings?

⁵ For like-minded reviews, see the Austin Chronicle and the New York Times.

References

Hasson U, Landesman O, Knappmeyer B, Vallines I, Rubin N, Heeger DJ. (2008). Neurocinematics: The Neuroscience of Film. Projections 2:1-26. [PDF]

Hasson U, Nir Y, Levy I, Fuhrmann G, Malach R. (2004). Intersubject Synchronization of Cortical Activity During Natural Vision. Science 303:1634-1640.

Montague PR, Berns GS, Cohen JD, McClure SM, Pagnoni G, Dhamala M, Wiest MC, Karpov I, King RD, Apple N, Fisher RE. (2002). Hyperscanning: simultaneous fMRI during linked social interactions. Neuroimage 16:1159-64.

Neurocinema, Neurocinematics

Is there a difference?



In The Neurocinema Collection™, we established that the term "neurocinema" doesn't really refer to movies with "Neuro" in the title or films about neurology. Instead, neuromarketers have have used the word in the following fashion:

Neurocinema is a new filmmaking process that studies a viewer's sensorimotor, cognitive, and affective response to film stimuli. Researchers use technologies such as functional magnetic resonance imaging (fMRI) to measure changes in activity in parts of the brain,electroencephalography (EEG) to measure activity in specific regional spectra of the brain response, and/or sensors to measure changes in one's physiological state (heart rate, respiratory rate, galvanic skin response) to learn exactly what scenes excite or disinterest the viewer.

There have been no peer-review studies on this methodology, only articles in the popular press (e.g., Wired.com and CNN.com). And from what was available in those reports, there was plenty to be neurocritical about.

On the other hand, Uri Hasson and his NYU colleagues published an article entitled Neurocinematics: The Neuroscience of Film in Projections: The Journal for Movies and Mind. Granted, that article is lacking the methodological details one would see in NeuroImage or Human Brain Mapping, but in fact the authors have published their work in prestigious journals (like Science and Neuron) without the "Neurocinematics" title.

In their Projections article, Hasson et al. (2008) state:

We propose that ISC [inter-subject correlation analysis] may be useful to film studies by providing a quantitative neuroscientific assessment of the impact of different styles of filmmaking on viewers’ brains, and a valuable method for the film industry to better assess its products. Finally, we suggest that this method brings together two separate and largely unrelated disciplines, cognitive neuroscience and film studies, and may open the way for a new interdisciplinary field of “neurocinematic” studies.

Hasson and colleagues first described the ISC method in their 2004 paper. In that study five subjects watched 30 min of The Good, The Bad, and The Ugly while laying supine in an MRI scanner. Unlike a typical fMRI experiment involving controlled presentation of individual pictures and performance of a categorization task, free viewing of a dynamic film is a more naturalistic situation. It also presents a more challenging data analysis problem. To tackle this, the researchers eschewed standard hypothesis-testing and adopted a purely data-driven approach to determine commonalities in brain activation across subjects.¹


Figure 1B (Hasson et al., 2008). The ISC analysis measures similarity in brain activity across viewers by comparing the response time course in each brain region from one viewer with the response time courses obtained in the same brain region from other viewers during movie watching.

The results (Hasson et al., 2004) demonstrated that...

Despite the free viewing and complex nature of the movie, we found an extensive and highly significant correlation across individuals watching the same movie. Thus, on average over 29% ± 10 SD of the cortical surface showed a highly significant intersubject correlation during the movie.....

Close inspection of this across-subject correlation revealed that the synchronization was far more extensive than the boundaries of well-known audiovisual sensory cortex defined with conventional mapping approach. ...the across-subject correlation covered most of the visual system, including early retinotopic areas as well as high-order object areas within the occipitotemporal and intraparietal cortex. Moreover, the correlation extended far beyond the visual and auditory cortices to the entire superior temporal (STS) and lateral sulcus (LS), retrosplenial gyrus, even secondary somatosensory regions in the postcentral sulcus, as well as multimodal areas in the inferior frontal gyrus and parts of the limbic system in the cingulate gyrus.

When corrected for non-selective elements, the intersubject correlation remained at 24% ± 8.5. The other 75% of the brain not "in sync" across subjects included parietal lobe areas (supramarginal and angular gyri) and the bulk of prefrontal cortex. Subcortical areas important for emotion and memory (amygdala and hippocampus) were not examined.

A second analysis was also performed, which took a "reverse-correlation" approach to examine activity in two well-know category-specific areas: the fusiform face area (for faces) and the parahippocampal place area (for buildings). This type of functional specialization was demonstrated in an earlier paper as well (Bartels & Zeki, 2004). In that study, the participants watched a James Bond movie (Tomorrow Never Dies). Activity in category-specific regions (for color, faces, language, and human bodies) was correlated with the perceived intensity of these specific attributes (as rated by a separate group of subjects who watched the same movie).

The most fascinating result in my opinion was obtained in subsequent experiments (described in Hasson et al., 2008) that compared the ISC for The Good, The Bad, and The Ugly to those observed for an episode of the TV series Alfred Hitchcock Presents (which is on Hulu!!!), an episode of the semi-improvised comedy Curb Your Enthusiasm, and a real-life unedited video shot in Washington Square Park. Not surprisingly,

The extent of ISC differed for the four movies (Figure 7A). The percentage of cortex exhibiting high ISC provided a measure of the overall effectiveness, or collective engagement power, of each movie to induce similar responses across viewers (Figure 7B). The Hitchcock episode (green) evoked similar responses across all viewers in over 65 percent of the cortex, indicating a high level of control of this particular episode on viewers’ minds. The high ISC was also extensive (45%) for the Good, the Bad and the Ugly (blue), but much less so (18%) for Curb Your Enthusiasm (red). Finally... the unstructured segment of reality (orange) induced high ISC only in a small fraction of the cortex (less than 5%).

Figure 7 (Hasson et al., 2008).

Glossing over the technical details [I didn't read the 5 other cited papers] and discrepancies between the 2004 and 2008 studies [divergence in ISC values of 25% vs. 45% for the same film], the implication is that different directors, and different filmmaking styles, exert varying levels of "control" over audio-visuo-higher-level cortical responses in the brains of the viewers:

The fact that Hitchcock was able to orchestrate the responses of so many different brain regions (Figure 7, green), turning them on and off at the same time across all viewers, may provide neuroscientific evidence for his notoriously famous ability to master and manipulate viewers’ minds. Hitchcock often liked to tell interviewers that for him “creation is based on an exact science of audience reactions” (Douchet 1985).

Different filmmakers strive to achieve different levels of control over their viewers’ reactions. Our findings provide empirical evidence to support the long-lasting distinction in film theory between films that remain faithful as much as possible to reality and those that seek to control or distort it.

The amount of control employed by filmmakers exists on continuum that ranges from real life --> documentaries --> art films --> Hollywood --> propaganda. The authors conclude with a discussion of collective engagement in film and suggest that it can be measured in an "objective" fashion using ISC. Overall, the 2008 Projections paper was a BOLD proposal for a true merger of art and science in academia.

Neurocinema, Neurocinematics? A semantic distinction perhaps, but the terms first appeared in different contexts. The former was used to describe an unvalidated filmmaking "process" [and underdeveloped commercial application] aimed squarely at attracting Hollywood megabucks, whereas the latter was used in a scholarly publication to describe a new field of inquiry. Will a merger (of sorts) be far behind? Or more to the point, has the NYU group applied for a patent yet?


Footnote

¹ The methods for this were pretty brief and largely contained within Footnote 15 of the paper:

15. In order to search for correlation between two corresponding regions across subjects (intersubject correlation), we first aligned all brains into Talairach coordinate system and used a Gaussian filter of 12 mm full width at half maximum value (FWHM) to the data... To remove preprocessing artifacts, we excluded the first and last 10 time points of the experiment from the analysis. We then used the time course of each voxel of the source subject as a GLM predictor for modeling the activity in the corresponding voxel of the target subject. Only voxels whose P value was no more than 0.05 (corrected) were considered significant.

References

Bartels A, Zeki S. (2004). Functional brain mapping during free viewing of natural scenes. Hum Brain Mapp. 21:75-85.

Hasson U, Landesman O, Knappmeyer B, Vallines I, Rubin N, Heeger DJ. (2008). Neurocinematics: The Neuroscience of Film. Projections 2:1-26. [PDF]



Hasson, U. et al. (2004). Intersubject Synchronization of Cortical Activity During Natural Vision. Science, 303 (5664), 1634-1640. DOI: 10.1126/science.1089506

Further Reading

Neurocinematics - The Valve - A Literary Organ

Neurocinematics - Neurophilosophy blog

Neurocinematics! Where Neuroscience Meets Filmmaking - NYU panel discussion held May 4, 2009

The Neurocinema Collection™

First poster for Joseph Kahn's adaptation of William Gibson's Neuromancer?


The term "neurocinema" has been in the news lately. What does it mean? Movies with the prefix "neuro" somewhere in the title?

Titles (20 Approx Matches)

		Neuro (2004)
		Neurosia - 50 Jahre pervers (1995) aka "Neurosia-Fifty Years of Perversion" - USA aka "Neurosia" - Germany (short title) aka "Neurosia - Who Shot Rosa von Praunheim" - USA (video box title)
		Labyrinth (1959) aka "Neurose" - Italy
		Revenge in the House of Usher (1982) aka "Neurosis"
		Neuromancer (2011)

Movies having to do with neurology, such as the NEURO CINEMA FESTIVAL sponsored by the San Francisco Neurological Society?

Awakenings (encephalitis, Parkinsons Disease)

Rainman (autistic disorder)

Away From Her (Alzheimers Disease)

M (psychotic disorder)

The Diving Bell and The Butterfly (stroke)

No, that's not right, either. "Neurocinema" has a short (and controversial) Wikipedia page:

Neurocinema is a new filmmaking process that studies a viewer's sensorimotor, cognitive, and affective response to film stimuli. Researchers use technologies such as functional magnetic resonance imaging (fMRI) to measure changes in activity in parts of the brain,electroencephalography (EEG) to measure activity in specific regional spectra of the brain response, and/or sensors to measure changes in one's physiological state (heart rate, respiratory rate, galvanic skin response) to learn exactly what scenes excite or disinterest the viewer.

The entry was originally marked for deletion on Sept. 25 (as a neologism with little coverage), but apparently it was reinstated after articles appeared in Wired.com and CNN.com. This minimalistic and poorly written entry is also a source of free publicity:

Peter Katz and MindSign Neuromarketing have done early studies into neurocinema that Wired.com and CNN has covered.

Dutifully following the links, here's what we learn from the CNN article:

Brain scans gauge horror flick fear factor

LONDON, England (CNN) -- Film producer Peter Katz doesn't just want his horror movies to scare you. He wants to pinpoint how frightened you are down to an exact moment in a scene.

To do that, he recently teamed up with researchers and used MRI scans of brain function to determine the degree of fright caused by certain scenes from his latest horror flick, "Pop Skull."

For the experiment, researchers at functional MRI research facility Mindsign Neuromarketing, based in San Diego, California, scanned the brain activity of a subject [NOTE: my emphasis] while she watched two scenes of his movie. Analyzing the data from the scan, they were able to pinpoint the exact moments when her brain was lit up with fear.

. . .

During Katz's experiment, researchers analyzed scans to identify the exact moment during each film scene that the viewer's amygdala -- the part of the brain linked to several emotions, including fear -- was activated, and to what degree.

Let's see where they went wrong scientifically: (1) Calling one subject "an experiment" -- was he making a movie just for her? (2) Saying fMRI can pinpoint the exact moment of anything -- there's a significant delay between initial neural firing and the peak of the hemodynamic response, which is estimated using a procedure that is not trivial for something as complex as an emotional response. (3) Using amygdala activity as a proxy for fear and thereby committing the cardinal sin of reverse inference (one cannot directly infer emotional state from the observed pattern of brain activity) -- didn't they learn from the op-ed neuroimaging fiasco in the New York Times ("This Is Your Brain on Politics")?


Then at Wired, Neurocinema Aims to Change the Way Movies are Made: [NOTE: or hyped]

Recently they finished their first full test with results that could change the way films are made. Yes, someone had to lie still in an MRI machine. The objective of the research, specifically, was to determine the brain response in the amygdala to watching scenes from the horror film Pop Skull. For those that don’t know, the amygdala is the emotional center of the brain. It’s involved in feelings of disgust, anger, lust and fear — all emotions especially elicited during a horror film. [NOTE: because it doesn't matter if your audience is feeling horny or disgusted instead of scared.]

. . .

For two sessions of 48 seconds and 68 seconds, a 24-year-old female watched two scenes from the movie while being scanned in a Siemens 3T MRI scanner. With a 20-second break in between three viewings of each scene (to refocus her eyes to center), the data was converted into a BrainMovie... and analyzed by the team at MindSign. What they saw (and what you can see in the movie) is that for most of the two movie scenes, the amygdala lit up like a Christmas tree out of fear. This activity was pinpointed to the frame, the exact scene and action that registered the response. For instance, “The scariest moment in Scene 1 came when the hand reaches further around the corner.” It is that precise.

Oh please spare me. I watched the BrainMovie and there were implausible jumps in activity from one frame to the next (compare "scary hand" at 2:42 to "scary hand again" at 2:48). Plus, don't you lose the element of surprise the second time you watch a specific scene? Who is going to see the infamous Alien chestburster scene the same way twice (i.e., 20 seconds after the first viewing)?

Then the Wired author interviewed film maker Katz and Dr. David Hubbard, "a board-certified neurologist who is the leading neurologist on the project." Although Dr. Hubbard has published respectable work on pain and headache using EMG, he has no papers at all using fMRI. Nonetheless, he is founder and chairman of The Hubbard Foundation for fMRI Research, "a charitable foundation supporting research and education in applied psychophysiology." He is also managing director of the Applied fMRI Institute, which presumably charges customers for "neuropsychological testing, neuromarketing and neurocinema, traditional academic research studies and explorations of meditation." No conflict of interest there. Oh wait, his education credits include STUDENT, Cognitive Science, University of California, San Diego, 2003-present. Good to know he's getting on the job fMRI training. This brain image doesn't instill a lot of confidence however given the extensive deactivation occurring outside the brain.

My final Google query was for MindSign Neuromarketing, whose motto is "Don’t rely on a focus group, or consumer’s ability to express their opinion about a product, let their minds speak for themselves." The organizational structure of MindSign was opaque at first, but I eventually discovered their scanning is done at "the cutting-edge Applied fMRI Institute, the only privately owned, market-friendly fMRI facility in the world."

In my view, the most successful aspect of this entire enterprise has been a boatload of uncritical coverage from the popular press.

For balanced blog coverage of the hype, see Neurovid: Neurocinema. And a neuromarketer presents a Scary Idea: Forget Focus Groups.

* With apologies to The Criterion Collection © 2008 for the title of this post.

It Hurts Less When I Can See It

Fig. 1 (Longo et al., 2009). The mirror box technique in which the subject has the experience of viewing their right hand, while in fact seeing their left hand reflected in a mirror.

Sight modifies somatosensation, by either enhancing or diminishing the subjective intensity of touch (Kennett et al., 2001) and pain (Ramachandran & Altschuler, 2009), respectively. These phenomena provide fascinating and lesser studied examples of crossmodal integration, or how signals from one sensory modality are combined with those of another to produce a unified percept. In an elegant series of experiments by Longo and colleagues, subjects who could see their own hand (either in a mirror or the real thing) reported less pain when exposed to the heat of a laser.


Laser ‘Pain Beam’ under development by the U.S. military. NOT used in the "elegant" laser evoked potential experiments.

Furthermore, an electrophysiological marker of pain was attenuated. This was measured from the EEG, time-locked to the application of the painful laser heat. These stimuli elicit a specific type of EEG response, called laser evoked potentials (LEPs). A sequence of three LEPs is generated in rapid succession, within the first 400 milliseconds after laser stimulation. These responses are called the N1, N2 and P2 potentials. As described in a review by Plaghki and Mouraux (2005),

Laser heat stimulators selectively activate Aδ and C-nociceptors ["pain receptors"] in the superficial layers of the skin. Their high power output produces steep heating ramps, which improve synchronization of afferent volleys and therefore allow the recording of time-locked events, such as laser-evoked brain potentials. Study of the electrical brain activity evoked by Aδ- and C-nociceptor afferent volleys revealed the existence of an extensive, sequentially activated, cortical network. These electrophysiological responses are modulated by stimulus-driven and, even more extensively, top-down processes.

These top-down processes include things like attention, expectation, and perhaps input from other sensory modalities. One advantage of LEPs is that you can determine exactly when in the pain processing stream these influences are active. Of greatest interest in this context is the N2-P2 complex, recorded at 195 milliseconds and 375 milliseconds after stimulation.


Fig. 5 (Longo et al., 2009). Grand mean LEPs recorded from electrode Cz in the three experiments and N2/P2 peak-to-peak amplitudes at Cz (bottom right). Error bars are 1 SEM.

The results demonstrated a cool new form of visually induced analgesia:

Looking at one's hand produced significant reductions of subjective intensity and unpleasantness of laser pain and in the amplitude of the N2/P2 complex.... These effects were observed both when the illusion of looking directly at the hand was induced with a mirror box (Exps. 1 and 3) and when participants viewed their hand directly during stimulation (Exp. 2). The reduction was specific to seeing one's own hand (Exp. 3).

What is the mechanism of action for these effects? First it's useful to know where in the brain the N2-P2 signals arise, because you can't tell from EEG alone. Plaghki and Mouraux review evidence from dipole models and invasive recordings, which have

consistently revealed the activation of an extensive bilateral cortical network, comprising the secondary somatosensory cortex (S2), the insular cortex and the anterior cingulate cortex.

It is noteworthy that the N1 response prior to the N2-P2 complex (not discussed here) is insensitive to the attentional and cognitive manipulations that affect the latter.

But how does visual input influence pain processing in the insula and anterior cingulate? How does this crossmodal inhibition occur? This is tricky, because any coherent explanation would have to account for visual enhancement of touch perception. Longo and colleagues speculate that inhibitory GABA-containing neurons might be responsible:

Could a common mechanism produce such divergent effects on touch and pain? One possibility would be a visually induced crossmodal activation of GABAergic interneurons. Injection of GABA antagonists increases the size of SI tactile receptive fields, suggesting that GABAergic interneurons function to sharpen tactile receptive fields, increasing tactile acuity. Conversely, GABA agonists are effective treatments for chronic central pain, suggesting that reduced GABAergic inhibition may be a major cause of chronic pain...

Both the present results showing analgesic effects of seeing the body and previous findings showing tactile enhancement (Kennett et al., 2001) could therefore be explained by visual modulation of somatosensory GABAergic interneurons. This speculation is supported by multisensory influences on cortical inhibition in other physiological systems. For example, viewing a hand extends the TMS-evoked silent period compared with viewing a fixation cross.

A related phenomenon was described by Mo Costandi in Distorting the body image affects perception of pain. Here, chronic pain patients viewed either magnified or "minified" versions of their affected arm while carrying out standarized motions. Subjective pain ratings were reported to be magnified or minified accordingly.

Finally, looking at images other than of one's own body can affect the perception of pain as well. For instance, viewing aesthically pleasing art during the application of laser heat stimuli reduced pain ratings and LEP amplitudes (de Tommaso et al., 2008), as covered by The Neurocritic in Pain & Paintings: Beholding Beauty Reduces Pain Perception and Laser Evoked Potentials.

In conclusion, Longo et al. note their results have possible implications for non-pharmacological treatments for pain:

First, the present results show an analgesic effect of vision of the body for acute, rather than chronic, pain. Second, several authors have suggested that mirror therapy may operate by promoting plastic reorganization within somatosensory map or by correcting a distorted body image through visual recalibration of proprioception [e.g. Ramachandran & Altschuler, 2009], yet our results demonstrate analgesic effects of seeing the body in healthy participants without body image distortion. Third, previous studies have generally involved voluntary movement of the unaffected limb, inducing the illusion of control over the affected hand. Therapeutic effects are typically attributed to the mirror-induced match between visually perceived movement and efferent commands specifying movement. The present results, however, suggest that qualitatively similar analgesic effects may result from simply seeing the hand, independent of movement or match between efferent and afferent signals.

Another application might be for the increasingly popular laser tattoo removal industry. Would having the client view the tattooed body part during the procedure lessen the perception of pain? Anyone who has tried (or would like to try) this experiment, please leave a comment on this post.



For the full on laser pain experience, watch Tattoo removal, no numbing cream. It's a straight edge dude getting XPROVENX removed from his neck. Other than screaming, his harshest utterance is "oh my gosh!"

References

de Tommaso M, Sardaro M, Livrea P. (2008). Aesthetic value of paintings affects pain thresholds. Conscious Cogn. 17:1152-62.

Kennett S, Taylor-Clarke M, Haggard P (2001). Noninformative vision improves the spatial resolution of touch in humans. Curr Biol 11:1188–1191.

Longo, M., Betti, V., Aglioti, S., & Haggard, P. (2009). Visually Induced Analgesia: Seeing the Body Reduces Pain. Journal of Neuroscience, 29 (39), 12125-12130. DOI: 10.1523/JNEUROSCI.3072-09.2009

Plaghki L, Mouraux A. (2005). EEG and laser stimulation as tools for pain research. Curr Opin Investig Drugs 6:58-64. PDF

Ramachandran VS, Altschuler EL. (2009). The use of visual feedback, in particular mirror visual feedback, in restoring brain function. Brain 132:1693-710.

Fact or Fiction? There ten times more glia than neurons in the brain.

"We only use 10% of our brains" is one of the most commonly held brain myths. But as the Neuroscience for Kids website tells us,

There is no scientific evidence to suggest that we use only 10% of our brains.

Neuroscientists, of course, already know that. But are there other false beliefs about the brain? Brain Mythology is a new column in the journal Brain Structure and Function, edited by Laszlo Zaborszky and Karl Zilles. In the first installment, Hilgetag and Barbas (2009) ask the question, Are there ten times more glia than neurons in the brain?

Neuroscience students take it for granted that there are many more glia than neurons in the brain. Neuroscience textbooks state with confidence: “Although there are many neurons in the human brain…, glia outnumber neurons by tenfold” (Bear et al. 2006) or, not to be outdone, even by “10–50 times”, as claimed in another text (Kandel et al. 2000). This fact is happily invoked by gliologists to promote the status of their field.

Damn those status-conscious gliologists! They've been leading us astray!

Given this well-accepted figure, we were surprised when our cell counts in the prefrontal cortex of the rhesus monkey turned up a glia-to-neuron ratio (GNR) of just about 1 (Dombrowski et al. 2001). There was some regional variation, but no prefrontal area had a GNR larger than 1.2. Maybe the proportion of glia is very different in other cortical regions or other parts of the brain, so that the overall ratio for the whole brain is much larger than 1? Classic studies, however, conducted by O’Kusky and Colonnier (1982) in the opposite pole of the brain, the visual cortex, had reported an even lower GNR of 0.5.

From Fig. 5A (Dombrowski et al., 2001). The ratio of glia/neurons in prefrontal areas or subdivisions of areas.

The origin of the glial dominance myth is not clear at all. Hilgetag and Barbas conclude by mentioning that...

Since the number of synapses increases faster than the number of neurons in larger brains, this affiliation of glia with the multitude of neural connection points may help explain... For example, in large brains such as the human brain... there may be as many as 1.4 astrocytes for each neuron, up from 0.33 in the rodent cortex (Nedergaard et al. 2003). Even that ratio, however, is still a long way from the myth of 10 times more glia than neurons, in any species.

Those species include humans of course, who are like monkeys with a nearly perfect 1:1 neuron:glia ratio [as noted by Jason Snyder].

References

Bear MF, Connors B, Paradiso M (2006). Neuroscience—exploring the brain, 3rd edn. Lippincott Williams & Wilkins, Philadelphia.

Dombrowski S, Hilgetag CC, Barbas H (2001). Quantitative architecture distinguishes prefrontal cortical systems in the rhesus monkey. Cereb Cortex 11:975–988.

Hilgetag, C., & Barbas, H. (2009). Are there ten times more glia than neurons in the brain? Brain Structure and Function, 213 (4-5), 365-366. DOI: 10.1007/s00429-009-0202-z

Kandel ER, Schwartz JH, Jessell TM (eds) (2000). Principles of neural science, nerve cells and behavior, 4th edn. McGraw-Hill, New York, p 22.

Nedergaard M, Ransom B, Goldman SA (2003). New roles for astrocytes: redefining the functional architecture of the brain. Trends Neurosci 26:523–530

O’Kusky J, Collonnier M (1982). A laminar analysis of the number of neurons, glia, and synapses in the adult cortex (area 17) of adult macaque monkeys. J Comp Neurol 210:278–290.


Image via EduSpaces.

A Highlighted Blog at Nature

The Neurocritic has been mentioned as a highlighted blog at nature.com, along with Good Math, Bad Math. Check out some of the other blogs in the Nature Network and beyond. Of the major non-OA (open access) publishers, NPG has been ahead of the curve in its online presence.

Thanks for the honor!

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