Fusiform Gyrus

Last month I reported on a finding that toddlers with autism spectrum disorder showed a strong preference for looking at moving shapes rather than active people. This lower interest in people is supported by a new imaging study involving 62 children aged 4-17, of whom 25 were diagnosed with autistic spectrum disorder and 20 were siblings of children with ASD.

In the study, participants were shown point-light displays (videos created by placing lights on the major joints of a person and filming them moving in the dark). Those with ASD showed reduced activity in specific regions (right amygdala, ventromedial prefrontal cortex, right posterior superior temporal sulcus, left ventrolateral prefrontal cortex, and the fusiform gyri) when they were watching a point-light display of biological motion compared with a display of moving dots. These same regions have also been implicated in previous research with adults with ASD.

Moreover, the severity of social deficits correlated with degrees of activity in the right pSTS specifically. More surprisingly, other brain regions (left dorsolateral prefrontal cortex, right inferior temporal gyrus, and a different part of the fusiform gyri) showed reduced activity in both the siblings group and the ASD group compared to controls. The sibling group also showed signs of compensatory activity, with some regions (right posterior temporal sulcus and a different part of the ventromedial prefrontal cortex) working harder than normal.

The implications of this will be somewhat controversial, and more research will be needed to verify these findings.

Older news items (pre-2010) brought over from the old website

August 2009

Common variation in gene linked to structural changes in the brain

Variations in the regions of the gene MECP2, previously associated with Retts Syndrome, autism, and mental retardation, has been found to be associated with changes in brain structure in both healthy individuals and patients with neurological and psychiatric disorders. The study used data from 289 healthy and psychotic subjects (the TOP study), and 655 healthy and demented patients (mostly Alzheimer's; from the ADNI study). The most significant genetic variation resulted in reduced surface area in the cortex (in particular in the cuneus, fusiform gyrus, pars triangularis), and was specific to males.

Joyner, A.H. et al. 2009. A common MECP2 haplotype associates with reduced cortical surface area in humans in two independent populations. Proceedings of the National Academy of Sciences, 106, 15483-15488; published online before print August 26, 2009, doi:10.1073/pnas.0901866106


April 2009

Research suggests words are seen as units and processed quickly

What exactly is going on in our brain when we read? Two new studies suggest the process is quicker and more direct than we thought. One study revealed that a region of the brain in the fusiform gyrus called the visual word form area (VWFA) recognizes words as whole units rather than letter by letter – words that differed in only one letter (e.g., "farm" and "form") produced changes in brain activity that were as profound as between completely different words (e.g., "farm" and "coat"), while incremental changes occurred in response to single-letter changes in made-up words. In another study, it was revealed that, rather than processing words in a slow, hierarchical way, we seem to process words quickly, through direct connections between visual and speech-processing systems. The first area to respond to text was the text recognition area in the occipito-temporal cortex, but it was followed within 15msec by both the VWFA and Broca's area (involved in speech processing). The results provide support for the idea that the brain has two rapid reading pathways (simultaneous rather than sequential): a lexical route using the VWFA and a sublexical route through Broca's area to the motor areas that control sound production (allowing us to sound out unfamiliar words).

Glezer, L.S., Jiang, X. & Riesenhuber, M. 2009. Evidence for Highly Selective Neuronal Tuning to Whole Words in the Visual Word Form Area. Neuron, 62 (2), 199-204.
Cornelissen, P.L. et al. 2009. Activation of the Left Inferior Frontal Gyrus in the First 200 ms of Reading: Evidence from Magnetoencephalography (MEG). PLoS ONE, 4(4), e5359. doi:10.1371/journal.pone.0005359


August 2006

No specialized face area

Another study has come out casting doubt on the idea that there is an area of the brain specialized for faces. The fusiform gyrus has been dubbed the "fusiform face area", but a detailed imaging study has revealed that different patches of neurons respond to different images. However, twice as many of the patches are predisposed to faces versus inanimate objects (cars and abstract sculptures), and patches that respond to faces outnumber those that respond to four-legged animals by 50%. But patches that respond to the same images are not physically connected, implying a "face area" may not even exist.

Grill-Spector, K., Sayres, R. & Ress, D. 2006. High-resolution imaging reveals highly selective nonface clusters in the fusiform face area. Nature Neuroscience, 9, 1177-1185.


May 2005

Brain networks change according to cognitive task

Using a newly released method to analyze functional magnetic resonance imaging, researchers have demonstrated that the interconnections between different parts of the brain are dynamic and not static. Moreover, the brain region that performs the integration of information shifts depending on the task being performed. The study involved two language tasks, in which subjects were asked to read individual words and then make a spelling or rhyming judgment. Imaging showed that the lateral temporal cortex (LTC) was active for the rhyming task, while the intraparietal sulcus (IPS) was active for the spelling task. The inferior frontal gyrus (IFG) and the fusiform gyrus (FG) were engaged by both tasks. However, Dynamic Causal Modeling (the new method for analyzing imaging data) revealed that the network took different configurations depending on the goal of the task, with each task preferentially strengthening the influences converging on the task-specific regions (LTC for rhyming, IPS for spelling). This suggests that task specific regions serve as convergence zones that integrate information from other parts of the brain. Additionally, switching between tasks led to changes in the influence of the IFG on the task-specific regions, suggesting the IFG plays a pivotal role in making task-specific regions more or less sensitive. This is consistent with previous studies showing that the IFG is active in many different language tasks and plays a role in integrating brain regions.

Bitan, T., Booth, J.R., Choy, J., Burman, D.D., Gitelman, D.R. & Mesulam, M-M. 2005. Shifts of Effective Connectivity within a Language Network during Rhyming and Spelling. Journal of Neuroscience, 25, 5397-5403.


December 2004

How the brain is wired for faces

The question of how special face recognition is — whether it is a process quite distinct from recognition of other objects, or whether we are simply highly practiced at this particular type of recognition — has been a subject of debate for some time. A new imaging study has concluded that the fusiform face area (FFA), a brain region crucially involved in face recognition, extracts configural information about faces rather than processing spatial information on the parts of faces. The study also indicated that the FFA is only involved in face recognition.

Yovel, G. & Kanwisher, N. 2004. Face Perception: Domain Specific, Not Process Specific. Neuron, 44 (5), 889–898.


How the brain recognizes a face

Face recognition involves at least three stages. An imaging study has now localized these stages to particular regions of the brain. It was found that the inferior occipital gyrus was particularly sensitive to slight physical changes in faces. The right fusiform gyrus (RFG), appeared to be involved in making a more general appraisal of the face and compares it to the brain's database of stored memories to see if it is someone familiar. The third activated region, the anterior temporal cortex (ATC), is believed to store facts about people and is thought to be an essential part of the identifying process.

Rotshtein, P., Henson, R.N.A., Treves, A., Driver, J. & Dolan, R.J. 2005. Morphing Marilyn into Maggie dissociates physical and identity face representations in the brain. Nature Neuroscience, 8, 107-113.


February 2004

Special training may help people with autism recognize faces

People with autism tend to activate object-related brain regions when they are viewing unfamiliar faces, rather than a specific face-processing region. They also tend to focus on particular features, such as a mustache or a pair of glasses. However, a new study has found that when people with autism look at a picture of a very familiar face, such as their mother's, their brain activity is similar to that of control subjects – involving the fusiform gyrus, a region in the brain's temporal lobe that is associated with face processing, rather than the inferior temporal gyrus, an area associated with objects. Use of the fusiform gyrus in recognizing faces is a process that starts early with non-autistic people, but does take time to develop (usually complete by age 12). The study indicates that the fusiform gyrus in autistic people does have the potential to function normally, but may need special training to operate properly.

Aylward, E. 2004. Functional MRI studies of face processing in adolescents and adults with autism: Role of experience. Paper presented February 14 at the annual meeting of the American Association for the Advancement of Science in Seattle.
Dawson, G. & Webb, S. 2004. Event related potentials reveal early abnormalities in face processing autism. Paper presented February 14 at the annual meeting of the American Association for the Advancement of Science in Seattle.


May 2002

Babies' experience with faces leads to narrowing of perception

A theory that infants' experience in viewing faces causes their brains (in particular an area of the cerebral cortex known as the fusiform gyrus) to "tune in" to the types of faces they see most often and tune out other types, has been given support from a study showing that 6-month-old babies were significantly better than both adults and 9-month-old babies in distinguishing the faces of monkeys. All groups were able to distinguish human faces from one another.

Pascalis, O., de Haan, M. & Nelson, C.A. 2002. Is Face Processing Species-Specific During the First Year of Life? Science, 296 (5571), 1321-1323.


November 2001

Differential effects of encoding strategy on brain activity patterns

Encoding and recognition of unfamiliar faces in young adults were examined using PET imaging to determine whether different encoding strategies would lead to differences in brain activity. It was found that encoding activated a primarily ventral system including bilateral temporal and fusiform regions and left prefrontal cortices, whereas recognition activated a primarily dorsal set of regions including right prefrontal and parietal areas. The type of encoding strategy produced different brain activity patterns. There was no effect of encoding strategy on brain activity during recognition. The left inferior prefrontal cortex was engaged during encoding regardless of strategy.

Bernstein, L.J., Beig, S., Siegenthaler, A.L. & Grady, C.L. 2002. The effect of encoding strategy on the neural correlates of memory for faces. Neuropsychologia, 40 (1), 86 - 98.


October 2001

Differences in face perception processing between autistic and normal adults

Imaging studies continue apace! Having established that that part of the brain known as the fusiform gyrus is important in picture naming, a new study further refines our understanding by studying the cerebral blood flow (CBF) changes in response to a picture naming task that varied on two dimensions: familiarity (or difficulty: hard vs easy) and category (tools vs animals). Results show that although familiarity effects are present in the frontal and left lateral posterior temporal cortex, they are absent from the fusiform gyrus. The authors conclude that the fusiform gyrus processes information relating to an object's structure, rather than its meaning. The blood flows suggest that it is the left posterior middle temporal gyrus that is involved in representing the object's meaning.

Whatmough, C., Chertkow, H., Murtha, S., & Hanratty, K. (2002). Dissociable brain regions process object meaning and object structure during picture naming. Neuropsychologia, 40, 174-186.

Different brain regions implicated in the representation of the structure and meaning of pictured objects

An imaging study compared activation patterns of adults with autism and normal control subjects during a face perception task. While autistic subjects could perform the face perception task, none of the regions supporting face processing in normals were found to be significantly active in the autistic subjects. Instead, in every autistic patient, faces maximally activated aberrant and individual-specific neural sites (e.g. frontal cortex, primary visual cortex, etc.), which was in contrast to the 100% consistency of maximal activation within the traditional fusiform face area (FFA) for every normal subject. It appears that, as compared with normal individuals, autistic individuals `see' faces utilizing different neural systems, with each patient doing so via a unique neural circuitry.

Pierce, K., Müller, R.-A., Ambrose, J., Allen, G. & Courchesne, E. (2001). Face processing occurs outside the fusiform `face area' in autism: evidence from functional MRI. Brain, 124 (10), 2059-2073.


July 2001

Why recognizing a face is easier when the race matches our own

We have known for a while that recognizing a face is easier when its owner's race matches our own. An imaging study now shows that greater activity in the brain's expert face-discrimination area occurs when the subject is viewing faces that belong to members of the same race as their own.

Golby, A. J., Gabrieli, J. D. E., Chiao, J. Y. & Eberhardt, J. L. 2001. Differential responses in the fusiform region to same-race and other-race faces. Nature Neuroscience, 4, 845 - 850.


parietotemporal region

May 2009

Brain's problem-solving function at work when we daydream

An imaging study has revealed that daydreaming is associated with an increase in activity in numerous brain regions, especially those regions associated with complex problem-solving. Until now it was thought that the brain's "default network" (which includes the medial prefrontal cortex, the posterior cingulate cortex and the temporoparietal junction) was the only part of the brain active when our minds wander. The new study has found that the "executive network" (including the lateral prefrontal cortex and the dorsal anterior cingulate cortex) is also active. Before this, it was thought that these networks weren’t active at the same time. It may be that mind wandering evokes a unique mental state that allows otherwise opposing networks to work in cooperation. It was also found that greater activation was associated with less awareness on the part of the subject that there mind was wandering.

Christoff, K. et al. 2009. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proceedings of the National Academy of Sciences, 106 (21), 8719-8724.


July 2008

Autism's social struggles due to disrupted communication networks in brain

And a timely imaging study has now provided the clearest evidence to date that synchronization in what might be termed the Theory of Mind network is impaired in autistic people. The Theory of Mind network (which includes the medial frontal gyrus, the anterior paracingulate, and the right temporoparietal junction) is responsible for processing the intentions and thoughts of others. In the study 12 high-functioning autistic adults and 12 controls viewed animated interacting geometric figures, and then asked to select the word from several choices that best described the interaction. The control subjects were consistently better at inferring the intention from the action than the participants with autism were. Brain scans revealed that synchronization between the frontal and posterior regions in the network was reliably lower in the group with autism. The autistic participants' brains also showed much lower activation levels in the frontal regions, and an independent assessment of their Theory of Mind abilities found these reliably correlated with activation in the right temporoparietal junction. The findings point to the need to develop interventions that could target this problem, and also indicate a way to measure an intervention’s effectiveness.

Kana, R.K. et al. 2008. Atypical frontal-posterior synchronization of Theory of Mind regions in autism during mental state attribution. Social Neuroscience, Published online ahead of print 3 July


June 2008

Remedial instruction can close gap between good, poor readers

A brain imaging study of poor readers has found that 100 hours of remedial instruction not only improved the skills of struggling readers, but also changed the way their brains activated when they comprehended written sentences. 25 fifth-graders who were poor readers worked in groups of three for an hour a day with a reading "personal trainer," a teacher specialized in administering a remedial reading program. The training included both word decoding exercises in which students were asked to recognize the word in its written form and tasks in using reading comprehension strategies. Brain scans while the children were reading revealed that the parietotemporal region — responsible for decoding the sounds of written language and assembling them into words and phrases that make up a sentence — was significantly less activated among the poor readers than in the control group. The increases in activation seen as a result of training were still evident, and even greater, a year later.
Although dyslexia is generally thought of as caused by difficulties in the visual perception of letters, leading to confusions between letters like "p" and "d", such difficulties occur in only about 10% of the cases. Most commonly, the problem lies in relating the visual form of a letter to its sound.

Meyler, A., Keller, T.A., Cherkassky, V.L., Gabrieli, J.D.E.  & Just, M.A.. 2008. Modifying the brain activation of poor readers during sentence comprehension with extended remedial instruction: A longitudinal study of neuroplasticity. Neuropsychologia, 46 (10), 2580-2592.