Abstract
Sensory impairments are a core feature of autism spectrum disorder (ASD). These impairments affect visual perception (Robertson and Baron-Cohen, 2017), and have been hypothesized to arise from imbalances in cortical excitatory and inhibitory activity (Rubenstein and Merzenich, 2003; Nelson and Valakh, 2015; Sohal and Rubenstein, 2019); however, there is little direct evidence testing this hypothesis in identified excitatory and inhibitory neurons during impairments of sensory perception. Several recent studies have examined cortical activity in transgenic mouse models of ASD (Goel et al., 2018; Antoine et al., 2019; Lazaro et al., 2019), but have provided conflicting evidence for excitatory versus inhibitory activity deficits. Here, we utilized a genetically relevant mouse model of ASD (CNTNAP2−/− knockout, KO; Arking et al., 2008; Penagarikano et al., 2011) and directly recorded putative excitatory and inhibitory population spiking in primary visual cortex (V1) while measuring visual perceptual behavior (Speed et al., 2019). We found quantitative impairments in the speed, accuracy, and contrast sensitivity of visual perception in KO mice. These impairments were simultaneously associated with elevated inhibitory and diminished excitatory neuron activity evoked by visual stimuli during behavior, along with aberrant 3 – 10 Hz oscillations in superficial cortical layers 2/3 (L2/3). These results establish that perceptual deficits relevant for ASD can arise from diminished sensory activity of excitatory neurons in feedforward layers of cortical circuits.
Footnotes
We have now examined psychometric performance as a function of stimulus contrast in both WT and KO mice. We find that KO mice have higher threshold contrasts and shallower slopes to saturating performance. During the same behavioral trials, we found reduced contrast sensitivity of excitatory and inhibitory neurons and L2/3 LFP responses in V1 of KO mice. These activity deficits were observed despite higher stimulus contrast thresholds. These new findings link neural activity deficits in specific cell types and cortical layers to impaired perception of visual contrast.