Cortical Dynamics: bottom-up and local effects

Abstract:

Adapting coding is ambiguous - the same response may have a different meaning depending on the history and the context of the stimulus. Using intracellular recordings in the brainstem of rats we found that changing the intensity of tactile stimulation has an opposite effect on the degree of adaptation in two major brainstem somatosensory subnuclei. Interestingly, using single cell and LFP recordings we found strong ‘signatures’ for these adaptation patterns in different cortical layers in a manner that was exactly predicted from previous in-vitro studies. We suggest that converging inputs from these ascending pathways in the cortex may partially solve the ambiguity of adapting coding. In the second part I will describe how the balance between excitation and inhibition is affected by adapting stimulation and how it is modulated by different cortical states. In particular, I will show that adaptation skews the balance toward excitation and that unexpectedly this process can facilitate cortical response to subsequent stimulation. In addition, by manipulating the depth of anesthesia we found that slow brain activity is characterized by enhanced inhibitory inputs but surprisingly without a significant effect on the magnitude of excitation, which suggests that despite the recurrent connectivity in the cortex some level of decoupling exists between cortical excitation and inhibition.