top of page

Brain Volume or Synaptic Density?
What is the main factor in autism?

Holanda, M. V. F., Da Silva Paiva, E., De Souza, L. N., Paiva, K. M., Oliveira, R. F., Tavares, É. a. F., De Góis Morais, P. L. A., De Andrade, A. M., Knackfuss, M. I., Nascimento, E. G. C. D., & De Paiva Cavalcanti, J. R. L. (2025).

Neurobiological basis of autism spectrum disorder: mini review. Frontiers in Psychology, 16, 1558081. https://doi.org/10.3389/fpsyg.2025.1558081

 

Matuskey, D., Yang, Y., Naganawa, M., Koohsari, S., Toyonaga, T., Gravel, P., Pittman, B., Torres, K., Pisani, L., Finn, C., Cramer-Benjamin, S., Herman, N., Rosenthal, L. H., Franke, C. J., Walicki, B. M., Esterlis, I., Skosnik, P., Radhakrishnan, R., Wolf, J. M., Nabulsi, N., … McPartland, J. C. (2025).

11C-UCB-J PET imaging is consistent with lower synaptic density in autistic adults. Molecular psychiatry, 30(4), 1610–1616. https://doi.org/10.1038/s41380-024-02776-2


Roy, D., & Uddin, L. Q. (2021). Atypical core-periphery brain dynamics in autism. Network neuroscience (Cambridge, Mass.), 5(2), 295–321. https://doi.org/10.1162/netn_a_00181

Introduction

Autism, more officially known as, autism spectrum disorder (ASD), is a neurodivergent symptom that is characterised by poor communication skills. The cause behind autism was thought to have been a result of environmental factors such as the growth environment of a developing child, but as younger children were also diagnosed with ASD, additional investigation was conducted on any genetic correlations. 

 

The brain chemistry and morphology of ASD is of particular interest, because it has two contradicting conditions in the neurobiological aspect. While brain volume was found to be bigger in young children diagnosed with ASD, recent research conducted by Dr. McPartland at the Yale school of medicine, highlighted that the neurobiological environment was not as simple as it looked (2025). 

 

Using positron emission tomography scans, Dr. McPartland’s group was able to see that the synaptic density was lower in an autistic adult's brain when compared to that of a neurotypical person.

​

unknown (2).png
Matuskey et al., 2025

As can be seen in the picture above, the synaptic density, highlighted by the color red, is smaller for autistic adults (bottom row) when compared to neurotypical adults (top row). This coincides with the fact that the rate of brain size growth actually decreases in autistic individuals as they grow past their childhood years (Roy and Uddin, 2021).

​

unknown (3).jpg
Holanda et al., 2025

From a perspective which focuses on ASD’s genetic origins, scientists have identified several genes which contribute to the development of ASD at a young age. While looking at the properties of each individual gene is interesting, that is for another blog post for another day. Rather I wish to focus on the fact that all four genes identified in the table above, had some connection to neuron and synaptic development, hence lending credence to the study results from Yale.

 

Lastly, it is important to add that there is no medication for ASD, as the reason for ASD is beyond a biochemical scope. As such, current treatment methods focus on nurturing the growth of the neurotic synapse through behavioral therapy with various medications providing substitutional relief.

bottom of page