Brain functioning and structure varies in individuals with autism spectrum disorder compared to individuals without ASD.
To learn about specific brain regions and their relation to ASD, review Part 1.
To learn about more specific brain information related to young children with ASD, review Part 2.
In this article, we will focus on adolescents and adults with ASD as the brain anatomy of individuals with ASD (as with all human beings) changes over time.
ADOLESCENTS AND ADULTS WITH ASD
Social communication and social interaction
The brain areas associated with social communication and interaction are referred to as the “social brain area” (Ha, et. al., 2015).
The social brain area includes the STS and its adjoining areas, such as:
- the middle temporal gyrus – which helps us make sense of the world (Davey, et. al., 2016),
- the fusiform gyrus (FG) – which has to do with face perception, object recognition, and reading (Weiner & Zilles, 2016),
- the amygdala – which helps to manage emotions,
- the medial prefrontal cortex (mPFC) – which is associated with decision making and memory consolidation (Euston, Gruber, & McNaughton, 2012),
- and inferior frontal gyrus (IFG) also known as Broca’s area – which is known for production and comprehension of language (Hampshire, et. al., 2010).
Differences in the structure and functioning of the social brain area are associated with the presence of differences in behavioral characteristics related to social communication and social interaction in individuals with ASD.
Theory of mind has to do with a person’s ability to understand the motivation and intentions of other people, to be able to predict what someone else may do or how they may respond and to imitate other people’s behaviors.
Differences in functioning of the mirror neuron system is related to theory of mind abilities. Being able to observe and imitate others behavior activates the right temporo-parietal junction which has been known to be associated with theory of mind.
Being able to take in information from another person’s face is important to human interactions and survival. We can also learn so much about a person by looking at their face, such as identifying their mood, their sex, estimating their age, and figuring out the direction of their gaze (Kanwisher & Yovel, 2006).
Being able to take in all of this information within a fraction of a second is essential for typical social interactions. This ability has played an important role for the survival of the human species.
Hypo-activation occurs in the bilateral fusiform face area which suggests that individuals with ASD do not experience as much activity in this area that is known for helping people read faces.
Restricted and repetitive patterns of behavior, interests, or activities
Differences in how individuals with ASD utilize executive functioning skills may be related to restricted and repetitive behaviors. Examples of executive functioning skills related to RRBs include the ability to control inhibition as well as cognitive flexibility.
RRBs are also associated with differences in cortical-basal ganglia circuitry which help us in the process of trial-and-error learning (Charlesworth, Warren, & Brainard, 2012).
RRBs are related to involuntary behavioral control which is present in the front striatal systems. Activity in the striatum helps us to integrate our behavior with the experience of reward (Báez-Mendoza & Schultz, 2013).
Response monitoring, which involves considering the outcome of one’s behaviors and then changing one’s behaviors accordingly to reach an ultimate goal, is related to the presence of RRBs. Response monitoring depends on the ACC. Individuals with ASD may have increased rostral ACC activation which is counterproductive to being able to evaluate one’s behaviors and then make error corrections accordingly (Polli, et. al., 2005).
Abnormal sensory processing is also related to RRBs.
The bilateral occipital cortex (which is the primary location where visual information is processed) and the anterior cingulate cortex (which is related to emotional regulation) may be more highly activated in adolescents and adults with ASD as compared to individuals without ASD. This may be partially why adolescents and adults with ASD often display emotional reactions in response to others who attempt to interfere with their RRBs.
The superior and middle frontal gyri – which relate to higher cognitive functions including working memory and spatial oriented processing – may be less activated in adolescents and adults with ASD as compared to individuals without ASD. (Fd Boisgueheneuc, Levy, Volle, Seassau, Duffau, Kinkingnehun, et al., 2006). This could influence the presence of RRBs in individuals with ASD due to the way in which they process things spatially as well as how they incorporate their behavior into working memory.
Ha, S., Sohn, I. J., Kim, N., Sim, H. J., & Cheon, K. A. (2015). Characteristics of Brains in Autism Spectrum Disorder: Structure, Function and Connectivity across the Lifespan. Experimental neurobiology, 24(4), 273–284. doi:10.5607/en.2015.24.4.273
Davey, J., Thompson, H. E., Hallam, G., Karapanagiotidis, T., Murphy, C., De Caso, I., … Jefferies, E. (2016). Exploring the role of the posterior middle temporal gyrus in semantic cognition: Integration of anterior temporal lobe with executive processes. NeuroImage, 137, 165–177. doi:10.1016/j.neuroimage.2016.05.051
Weiner, K. S., & Zilles, K. (2016). The anatomical and functional specialization of the fusiform gyrus. Neuropsychologia, 83, 48–62. doi:10.1016/j.neuropsychologia.2015.06.033
Euston, D. R., Gruber, A. J., & McNaughton, B. L. (2012). The role of medial prefrontal cortex in memory and decision making. Neuron, 76(6), 1057–1070. doi:10.1016/j.neuron.2012.12.002
Hampshire, A., Chamberlain, S. R., Monti, M. M., Duncan, J., & Owen, A. M. (2010). The role of the right inferior frontal gyrus: inhibition and attentional control. NeuroImage, 50(3), 1313–1319. doi:10.1016/j.neuroimage.2009.12.109
Kanwisher, N., & Yovel, G. (2006). The fusiform face area: a cortical region specialized for the perception of faces. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 361(1476), 2109–2128. doi:10.1098/rstb.2006.1934
Charlesworth, J. D., Warren, T. L., & Brainard, M. S. (2012). Covert skill learning in a cortical-basal ganglia circuit. Nature, 486(7402), 251–255. doi:10.1038/nature11078
Báez-Mendoza, R., & Schultz, W. (2013). The role of the striatum in social behavior. Frontiers in neuroscience, 7, 233. doi:10.3389/fnins.2013.00233
Polli, F. E., Barton, J. J., Cain, M. S., Thakkar, K. N., Rauch, S. L., & Manoach, D. S. (2005). Rostral and dorsal anterior cingulate cortex make dissociable contributions during antisaccade error commission. Proceedings of the National Academy of Sciences of the United States of America, 102(43), 15700–15705. doi:10.1073/pnas.0503657102
Fd Boisgueheneuc, Levy R, Volle E, Seassau M, Duffau H, Kinkingnehun S, et al. Functions of the left superior frontal gyrus in humans: a lesion study. Brain. 2006;129(12):3315–28. [PubMed] [Google Scholar]