Symptom Provocation of Obsessive-Compulsive Symptoms in Tourette Disorder and its Neural Correlates

It is known that Tourette Syndrome (TS) is often accompanied by obsessive-compulsive disorder (OCD) and there do exist a lot of similarities among symptoms such as tics and obsessive-compulsive symptoms (OCS; Bhikram, Crawley, Arnold, Abi-Jaoude, and Sandor, 2020).

Symptom provocation while participants underwent fMRI was used in order to identify its neural substrates (Bhikram et al., 2020). Symptom provoking pictures concerning washing, checking, and symmetry in addition to neutral and disgust pictures were used. There were three different participan groups created for comparison, These were TS with severe/moderate OCS, TS with absent/mild OCS, and healthy control participants.

The paradigm that the investigators used was found to be effective in inducing subjective anxiety of higher magnitude in TS as compared to healthy controls In the conditions with symptom provocation. Higher subjective anxiety was not found in the neutral and disgust conditions (Bhikram et al., 2020).

Within the group of TS participants, there was found a negative relationship among OCS severity and activation in brain areas such as the supramarginal gyrus, precuneus, and visual processing areas, which was found to be common in all symptom provocation conditions. Furthermore, for exept the provocation condition concerning washing, there were found negative relationships among OCS severity and activation of the precentral gyrus, SMA, and IFG to be found across all provocation conditions. 

The severity of tics was only related to activation of the anterior cingulate cortex concerning the symmetry symptom provocation condition (Bhikram et al., 2020).

Object Perception in Autism Spectrum

Perceptual organization at the ventral visual stream was investigated in participants with autism spectrum disorder ( ASD) adolescents and healthy control participants (Sapey-Triomphe, Boets, Van Eylen, Noens, Sunnaert, Steyaert, and Wagemans, 2020).

Objects were presented that did differ in perceptual organization. It was investigated if ASD participants would show diminished top-down modulation.

The results show that at the behavioral level both participant groups were comparable at identifying shapes that were embedded in random oriented Gabor pieces. Accuracy and reaction time were not affected whether the shapes were shown by only contour, only texture, or both contour and texture. Furthermore, whether the objects were recognizable or not did also not differ between the two groups.

Brain activation patterns were not very different among the groups and detection of the shapes was found to be associated with involvement of brain regions from low-level to high-level regions at the ventral visual stream. Stimuli that were meaningful, that is, objects that were recognizable, were found to be associated with larger activation in the LOC as well as in the middle occipital gyri in the participants with ASD.

Top-down modulation and functional connections among areas of the ventral visual stream was present at higher cortical hierarchy but not the lower in ASD participants as compared to healthy control participants.

Accordingly, ASD participants might get less top-down signs from brain areas at the higher level as compared to healthy control participants. The result might be that there will be diminished facilitation as well as more difficulties for the identification of objects in ASD. Global processing was found to be normal in ASD (Sapey-Triomphe et al., 2020).