Intrinsic neural timescales in autism spectrum disorder and schizophrenia. A replication and direct comparison study.

Intrinsic neural timescales (INT) reflect the duration for which brain areas store information. A posterior-anterior hierarchy of increasingly longer INT has been revealed in both typically developed individuals (TD), as well as persons diagnosed with autism spectrum disorder (ASD) and schizophrenia (SZ), though INT are, overall, shorter in both patient groups. In the present study, we aimed to replicate previously reported group differences by comparing INT of TD to ASD and SZ. We partially replicated the previously reported result, showing reduced INT in the left lateral occipital gyrus and the right post-central gyrus in SZ compared to TD. We also directly compared the INT of the two patient groups and found that these same two areas show significantly reduced INT in SZ compared to ASD. Previously reported correlations between INT and symptom severity were not replicated in the current project. Our findings serve to circumscribe the brain areas that can potentially play a determinant role in observed sensory peculiarities in ASD and SZ.

Reduced intrinsic neural timescales in schizophrenia along posterior parietal and occipital areas.

We computed intrinsic neural timescales (INT) based on resting-state functional magnetic resonance imaging (rsfMRI) data of healthy controls (HC) and patients with schizophrenia spectrum disorder (SZ) from three independently collected samples. Five clusters showed decreased INT in SZ compared to HC in all three samples: right occipital fusiform gyrus (rOFG), left superior occipital gyrus (lSOG), right superior occipital gyrus (rSOG), left lateral occipital cortex (lLOC) and right postcentral gyrus (rPG). In other words, it appears that sensory information in visual and posterior parietal areas is stored for reduced lengths of time in SZ compared to HC. Finally, we found that symptom severity appears to modulate INT of these areas in SZ.

Effective Connectivity of the Hippocampus Can Differentiate Patients with Schizophrenia from Healthy Controls: A Spectral DCM Approach.

We applied spectral dynamic causal modelling (Friston et al. in Neuroimage 94:396-407. https://doi.org/10.1016/j.neuroimage.2013.12.009 , 2014) to analyze the effective connectivity differences between the nodes of three resting state networks (i.e. default mode network, salience network and dorsal attention network) in a dataset of 31 male healthy controls (HC) and 25 male patients with a diagnosis of schizophrenia (SZ). Patients showed increased directed connectivity from the left hippocampus (LHC) to the: dorsal anterior cingulate cortex (DACC), right anterior insula (RAI), left frontal eye fields and the bilateral inferior parietal sulcus (LIPS & RIPS), as well as increased connectivity from the right hippocampus (RHC) to the: bilateral anterior insula (LAI & RAI), right frontal eye fields and RIPS. In SZ, negative symptoms predicted the connectivity strengths from the LHC to: the DACC, the left inferior parietal sulcus (LIPAR) and the RHC, while positive symptoms predicted the connectivity strengths from the LHC to the LIPAR and from the RHC to the LHC. These results reinforce the crucial role of hippocampus dysconnectivity in SZ pathology and its potential as a biomarker of disease severity.

Reduced spontaneous perspective taking in schizophrenia.

Judgments about another person's visual perspective are impaired when the self-perspective is inconsistent with the other-perspective. This is a robust finding in healthy samples as well as in schizophrenia (SZ). Studies show evidence for the existence of a reverse effect, where an inconsistent other-perspective impairs the self-perspective. Such spontaneous perspective taking processes are not yet explored in SZ. In the current fMRI experiment, 24 healthy and 24 schizophrenic participants performed a visual perspective taking task in the scanner. Either a social or a non-social stimulus was presented and their visual perspectives were consistent or inconsistent with the self-perspective of the participant. We replicated previous findings showing that healthy participants show increased reaction times when the human avatar's perspective is inconsistent to the self-perspective. Patients with SZ, however, did not show this effect, neither in the social nor in the non-social condition. BOLD responses revealed similar patterns in occipital areas and group differences were identified in the middle occipital gyrus. These findings suggest that patients with SZ are less likely to spontaneously compute the visual perspectives of others.