This chapter covers a spectrum of models for both chemical and electrical synapses. Different levels of detail are delineated in terms of model complexity and suitability for different situations. These range from empirical models of voltage waveforms to more detailed kinetic schemes, and to complex stochastic models, including vesicle recycling and release. Simple static models that produce the same postsynaptic response for every presynaptic action potential are compared with more realistic models incorporating short-term dynamics that produce facilitation and depression of the postsynaptic response. Different postsynaptic receptor-mediated excitatory and inhibitory chemical synapses are described. Electrical connections formed by gap junctions are considered.

This chapter applies a perspective from biophysically grounded computational modeling to explore how the intrinsic properties of thalamic microcircuits support the computational roles that the thalamus plays in perceptual and cognitive functions. A key focus is on the modeling of neurophysiological activity in the thalamus as nonlinear dynamical systems. Dynamical modeling can give insight into thalamic function across levels of analysis, including cellular channel properties, synaptic plasticity, and anatomical connectivity. This chapter reviews how the interplay between cellular and circuit mechanisms supports thalamic contributions to neural oscillations, regulation of brain state, top-down attentional control of sensory processing, and other cognitive functions. Understanding circuit function through biophysically grounded computational modeling and dynamical systems perspectives can also provide insight into how cellular and synaptic alterations caused by pharmacology or disease can impair thalamic function.

The somatosensory thalamocortical system has proven a tractable model for dissecting how different neuronal populations sculpt bidirectional information exchange between the thalamus and the cortex. This chapter reviews corticothalamic (CT) pathways from layers 5 (L5) and 6 (L6) of the primary somatosensory (S1) cortex to first-order ventroposterior (VP) and higher-order posterior medial (POm) somatosensory thalamic nuclei. With a focus on insights gained from recent cell-type–specific approaches in rodent models, we contrast L5 and L6 CT pathways at the scales of network architecture, anatomical connectivity, and physiological characteristics. We further compare the distinct feedforward inhibitory circuits engaged by L6 and L5 CT pathways, which involve the thalamic reticular nucleus and extrathalamic inhibitory nuclei, respectively. Where data exist, we discuss short- and long-term synaptic dynamics of the specific CT circuits. We close with a discussion of the proposed functions of these distinct pathways in conveying “top-down” cortical signals for both the modulation of thalamic processing of sensory information and the transmission of information between cortical regions.