Showing papers by "Neeraj Jain published in 2016"
TL;DR: These and other features of the cortical input pattern suggest that RMA has a distinct, and more of integrative functional role compared with M1.
Abstract: Rats have a complete body representation in the primary motor cortex (M1). Rostrally there are additional representations of the forelimb and whiskers, called the rostral forelimb area (RFA) and the rostral whisker area (RWA). Recently we showed that sources of thalamic inputs to RFA and RWA are similar, but they are different from those for the caudal forelimb area (CFA) and the caudal whisker area (CWA) of M1 (Mohammed and Jain [2014] J Comp Neurol 522:528-545). We proposed that RWA and RFA are part of a second motor area, the rostral motor area (RMA). Here we report ipsilateral cortical connections of whisker representation in RMA, and compare them with connections of CWA. Connections of RFA, CFA, and the caudally located hindlimb area (CHA), which is a part of M1, were determined for comparison. The most distinctive features of cortical inputs to RWA compared with CWA include lack of inputs from the face region of the primary somatosensory cortex (S1), and only about half as much inputs from S1 compared with the lateral somatosensory areas S2 (second somatosensory area) and the parietal ventral area (PV). A similar pattern of inputs is seen for CFA and RFA, with RFA receiving smaller proportion of inputs from the forepaw region of S1 compared with CFA, and receiving fewer inputs from S1 compared with those from S2. These and other features of the cortical input pattern suggest that RMA has a distinct, and more of integrative functional role compared with M1. J. Comp. Neurol. 524:3104-3123, 2016. © 2016 Wiley Periodicals, Inc.
17 citations
TL;DR: The characteristics of widespread suppressive or inhibitory response properties with and without initial facilitative or excitatory responses add to the growing evidence that neurons in primary somatosensory cortex provide essential processing for integrating sensory stimulation from across the hand.
Abstract: In somatosensory cortex, tactile stimulation within the neuronal receptive field (RF) typically evokes a transient excitatory response with or without postexcitatory inhibition. Here, we describe neuronal responses in which stimulation on the hand is followed by suppression of the ongoing discharge. With the use of 16-channel microelectrode arrays implanted in the hand representation of primary somatosensory cortex of New World monkeys and prosimian galagos, we recorded neuronal responses from single units and neuron clusters. In 66% of our sample, neuron activity tended to display suppression of firing when regions of skin outside of the excitatory RF were stimulated. In a small proportion of neurons, single-site indentations suppressed firing without initial increases in response to any of the tested sites on the hand. Latencies of suppressive responses to skin indentation (usually 12-34 ms) were similar to excitatory response latencies. The duration of inhibition varied across neurons. Although most observations were from anesthetized animals, we also found similar neuron response properties in one awake galago. Notably, suppression of ongoing neuronal activity did not require conditioning stimuli or multi-site stimulation. The suppressive effects were generally seen following single-site skin indentations outside of the neuron's minimal RF and typically on different digits and palm pads, which have not often been studied in this context. Overall, the characteristics of widespread suppressive or inhibitory response properties with and without initial facilitative or excitatory responses add to the growing evidence that neurons in primary somatosensory cortex provide essential processing for integrating sensory stimulation from across the hand.
14 citations