Motor cortex gates vibrissal responses in a thalamocortical projection pathway.
ABSTRACT Higher-order thalamic nuclei receive input from both the cerebral cortex and prethalamic sensory pathways. However, at rest these nuclei appear silent due to inhibitory input from extrathalamic regions, and it has therefore remained unclear how sensory gating of these nuclei takes place. In the rodent, the ventral division of the zona incerta (ZIv) serves as a relay station within the paralemniscal thalamocortical projection pathway for whisker-driven motor activity. Most, perhaps all, ZIv neurons are GABAergic, and recent studies have shown that these cells participate in a feedforward inhibitory circuit that blocks sensory transmission in the thalamus. The present study provides evidence that the stimulation of the vibrissa motor cortex suppresses vibrissal responses in ZIv via an intra-incertal GABAergic circuit. These results provide support for the proposal that sensory transmission operates via a top-down disinhibitory mechanism that is contingent on motor activity.
Article: Spiking in primary somatosensory cortex during natural whisking in awake head-restrained rats is cell-type specific.[show abstract] [hide abstract]
ABSTRACT: Sensation involves active movement of sensory organs, but it remains unknown how position or movement of sensory organs is encoded in cortex. In the rat whisker system, each whisker is represented by an individual cortical (barrel) column. Here, we quantified in awake, head-fixed rats the impact of natural whisker movements on action potential frequencies of single (identified) neurons located in different layers of somatosensory (barrel) cortex. In all layers, we found only weak correlations between spiking and whisker position or velocity. Conversely, whisking significantly increased spiking rate in a subset of neurons located preferentially in layer 5A. This finding suggests that whisker movement could be encoded by population responses of neurons within all layers and by single slender-tufted pyramids in layer 5A.Proceedings of the National Academy of Sciences 09/2009; 106(38):16446-50. · 9.68 Impact Factor
Article: Dissociable processes of cognitive control during error and non-error conflicts: a study of the stop signal task.[show abstract] [hide abstract]
ABSTRACT: Conflict detection and subsequent behavioral adjustment are critical to daily life, and how this process is controlled has been increasingly of interest. A medial cortical region which includes the anterior cingulate cortex (ACC) has been theorized to act as a conflict detector that can direct prefrontal activity for behavioral adjustments. This conflict monitoring hypothesis was supported by many imaging studies of the Stroop task, with a focus on non-error processes. Here we sought to examine whether this circuit could be generalized to the stop signal task (SST), another behavioral paradigm widely used to study cognitive control. In particular, with a procedure to elicit errors in the SST, we examined whether error and non-error control were mediated by the same pathways. In functional magnetic resonance imaging of 60 healthy adults, we demonstrated that the medial cortical activity during stop success (SS) as compared to go success (G) trials is correlated with increased prefrontal activity in post-stop SS as compared to post-go SS trials, though this correlation was not specific to the medial cortical region. Furthermore, thalamic and insular rather than medial cortical activation during stop error (SE) as compared to G trials correlated with increased prefrontal activity in post-stop SS as compared to post-go SS trials. Taken together, these new findings challenge a specific role of the ACC and support distinct pathways for error and non-error conflict processing in cognitive control.PLoS ONE 01/2010; 5(10):e13155. · 4.09 Impact Factor
Article: Laminar analysis of excitatory local circuits in vibrissal motor and sensory cortical areas.[show abstract] [hide abstract]
ABSTRACT: Rodents move their whiskers to locate and identify objects. Cortical areas involved in vibrissal somatosensation and sensorimotor integration include the vibrissal area of the primary motor cortex (vM1), primary somatosensory cortex (vS1; barrel cortex), and secondary somatosensory cortex (S2). We mapped local excitatory pathways in each area across all cortical layers using glutamate uncaging and laser scanning photostimulation. We analyzed these maps to derive laminar connectivity matrices describing the average strengths of pathways between individual neurons in different layers and between entire cortical layers. In vM1, the strongest projection was L2/3→L5. In vS1, strong projections were L2/3→L5 and L4→L3. L6 input and output were weak in both areas. In S2, L2/3→L5 exceeded the strength of the ascending L4→L3 projection, and local input to L6 was prominent. The most conserved pathways were L2/3→L5, and the most variable were L4→L2/3 and pathways involving L6. Local excitatory circuits in different cortical areas are organized around a prominent descending pathway from L2/3→L5, suggesting that sensory cortices are elaborations on a basic motor cortex-like plan.PLoS Biology 01/2011; 9(1):e1000572. · 11.45 Impact Factor