Category: Brain Science

Diminished social orientation and reduced direct eye contact with other people are well known symptoms of people with Autism Spectrum Disorders. A recent study asked if the reduced eye contact is due to reduced social orientation towards the eyes or an increase in active avoidance.

The study “Atypical reflexive gaze patterns on emotional faces in autism spectrum disorders” was published September 15, 2010 in The Journal of Neuroscience.

Participants looked at neutral, happy, fearful faces with their gaze initially focused on the eyes or the mouth. Eye movement was recorded and the participants were asked to report the emotional category of the face.

Reduced direct eye contact in individuals with Autism Spectrum Disorders was confirmed. In addition, a significant correlation between the severity of an individual’s social impairments and their gaze pattern was observed. Participants with Autism Spectrum Disorders who were better at correctly classifying emotion also had a greater preference for looking at the eye region.

When the researchers looked at how fast individuals redirected their gaze they found that the individuals with Autism Spectrum Disorders moved their gaze away from eye contact faster than control subjects. This is suggestive of an avoidance mechanism active in individuals with Autism Spectrum Disorders.

In summary, it seems that those with Autism Spectrum Disorders show both reduced social orientation towards the eyes and an increase in active avoidance of eye contact. It’ll be important for future research to try to define specific brain mechanisms underlying each of these characteristic symptoms.

Other related blog posts:

Autism and the Brain: Recent Results from Brain Imaging Studies

Research has shown that babies do an incredible amount of language processing even before they reach their first birthday. The review “Brain Mechanisms in Early Language Acquisition” published September 9, 2010 in Neuron summarizes some of these data.

The auditory sensory areas in brains of newborns are activated by speech and a number of studies have shown that they are already acquiring language skills and their neural circuitry is influenced. However, the 0 to about 3 month old infant’s motor speech areas are not yet activated.

Speech directed to babies about 3 months old activates their motor speech areas in addition to their auditory sensory areas. At this point the infant begins acquiring sensory and motor language skills.

Social interaction is necessary to acquiring language skills in addition to hearing speech and using motor skills to make speech sounds. An infant exposed to a new language through social interaction shows robust learning. In contrast, infants exposed to the same material but through video or audio tapes show no learning at all.

An infant’s social behavior can be linked to their ability to learn new language material. Babies that are more actively engaged in the learning experience as measured by their gaze progress faster.

Very young babies (less than 1 year old) can seem like they’re doing very little. Don’t be fooled! They’re very active and are counting on you to baby-talk to them.

Since at least the 1960s brain scientists have thought that nerve cell dendrites may discriminate amongst sequences of signal inputs that vary across time and space but experimental methods were not able to control and measure signals at the very small time (submillisecond) and space (submicron) precision necessary to test the idea.

New experimental techniques using two-photon glutamate uncaging in identified dendritic spines now enable the idea to be directly investigated. The paper “Dendritic Discrimination of Temporal Input Sequences in Cortical Neurons” published September 24, 2010 issue of Science tests to see if dendrites discriminate between different temporal and spacial input sequences.

Indeed, the result is yes and some of the specific mechanisms underlying the discrimination are exposed. Impedance along the dendritic shaft was shown to be important and NMDA receptors were shown to be crucial. In fact, the research showed that a large dynamic range provided by NMDA receptor activation enabled high fidelity discrimination between different spatial-temporal sequences whether the input was all on the same dendritic branch or dispersed across the dendritic tree.

As neuroscientists demonstrate the computational complexity of axon terminals and dendritic trees I expect the focus for those interested in how signal processing is carried out in the brain to move from the neuron to the microstructure known as the neuropil.