Clarissa Whitmire

The internal representation of the outside world is built on patterns of neural activity, commonly referred to as the ‘neural code’. While we often model the neural code as a linear mapping from stimulus to spikes, it is actually extremely complicated and nonlinear even very early in the sensory pathway. In particular, the neural code explodes in complexity at the thalamocortical circuit. The thalamocortical circuit is a key component of sensory perception. Nearly all sensory information travels through the thalamus before reaching cortex. Further, the thalamus acts as a hub for both cortical and subcortical circuits, suggesting it is an integrative structure. While traditionally labelled as a relay nucleus, it is now proposed that the thalamus plays an important role in transforming sensory information traveling from the sensory periphery to primary sensory cortex. This has led to the hypothesis that the thalamus acts as a gate for sensory information flow from the external world to the representation in cortex.

Dr. Whitmire has made major contributions to the mechanisms of thalamic encoding using a combination of neural recording and stimulation. Her work has identified state-dependent encoding as a mechanism by which information is dynamically represented in somatosensory thalamus. Using a combination of experimental paradigms and computational models, she proposed a novel mechanism of dynamic thalamic gating whereby the encoding of a sensory signal is modulated by the ongoing sensory stimulus. Specifically, I found that sensory adaptation (Whitmire & Stanley 2016) leads to a shift in the thalamic firing mode from burst firing mode to tonic firing mode. Consistent with thalamic bursting acting as a “wake-up call” to cortex, I found that burst spikes are more detectable and less discriminable than tonic spikes (Whitmire et al. 2016) but can fire with less temporal precision (Whitmire et al. 2021). Changes to the temporal firing properties in the thalamus directly impact the cortical representation and could have broad implications for sensation and action.

To further dissect how the highly interconnected thalamocortical loop is operating, she has also developed methods to causally manipulate neural activity. These include the characterization of artificial stimulation of thalamic synchrony and cortical activation (Millard et al. 2015), the use of artificial stimulation to quantify the role of thalamic state in cortical dynamics independent of subthalamic adaptation (Whitmire et al. 2017), the development of closed loop optogenetic control to drive desired thalamic firing patterns (Newman et al. 2015, Bolus et al. 2018), and an analytic framework for assessing synaptic connectivity (Liew et al. 2021). In each of these studies, she has developed methods to explicitly quantify the encoding of somatosensory information in the thalamocortical circuit and to develop a framework to control information flow on the single neuron level through artificial manipulations.

Further, Dr. Whitmire is interested in expanding the understanding of encoding properties across thalamocortical circuits. Across sensory modalities, thalamocortical pathways have multiple parallel representations. She has recently shown that this is also true for somatosensation as the somatosensory thalamus can actually be separated into two non-overlapping neuronal populations that are defined by their cortical projection target (Bokiniec et al. 2023). The anterior somatosensory pathway travels through the ventrobasal thalamus to the primary somatosensory cortex while the posterior pathway travels through the posterior triangular nucleus of the thalamus to the posterior insular cortex (Leva & Whitmire 2023). The duality of the somatosensory pathway presents an interesting testbed for investigating canonical circuit function in the thalamocortical circuit.