Exploring the specific time course of interhemispheric inhibition between the human primary sensory cortices

Title: Exploring the specific time course of interhemispheric inhibition between the human primary sensory cortices

Journal: J Neurophysiol (2014) 112: 1470 –1476.

Link: https://journals.physiology.org/doi/pdf/10.1152/jn.00074.2014

Comments: Brain asymmetries in humans are known to be more pronounced than in other animals, with some degree of hemispheric specialization seen in all higher functions including memory, learning, perception, complex motor skills, etc. Inter-hemispheric inhibition (IHI) is a general feature of mammalian neural systems observed in motor cortex. Several research studies have confirmed that IHI is largely mediated by transcallosal pathways. IHI can be demonstrated by measuring reduction in the evoked potential for conditioned stimulus in contralateral side preceding the test stimulus delivered to ipsilateral side.

The primary somatosensory cortex (S1) plays a critical role in the integration of sensory and motor signals for skilled movement. However, the mechanism of IHI in S1 is still not fully understood. This paper examined the change in cortical sensory evoked potential recorded over the right S1 following activation of the homologous left S1 due to somatosensory IHI. The authors concluded that the IHI in S1 depends on the temporal asynchrony of the bilateral input and the specific timing is reflective of a transcallosal mechanism as is seen in the case of the motor system. How best to modulate IHI is a likely avenue of interest in stroke rehabilitation.