Our lab is interested in how neurons in the auditory thalamus and cortex represent features of sound in normal and pathological conditions. We are interested in the representation of sound at various levels - behavioral responses to sound, evoked potentials from the entire auditory cortex, in vivo discharge patterns to sound from a single neuron as well as intrinsic and synaptic currents produced by neurons involved in the generation of those patterns in vitro. In doing so we want to work towards bridging the gap between macro level events like behavior and synaptic events at the molecular level
I. Functional Organization of the MGB and Cortex
Neural representations of temporal modulation are differentially distributed within subdivisions of the auditory thalamus, or medial geniculate body (MGB). Neurons in the core regions of auditory thalamus such as the ventral division (V) often produce stimulus-synchronized discharges that are phase-locked to a temporally modulated stimulus. Neurons in a belt region of auditory thalamus, the caudodorsal division (CD), infrequently produce synchronized responses. Instead, rapid temporal modulations are represented by changes in firing rate that are not stimulus-synchronized (Bartlett and Wang 2007). Shown above is a figure summarizing those results. We seek to further reveal the ways in which sound features are parsed into parallel but interacting pathways in the auditory thalamus and cortex.
Ryan Verner is currently assessing the functional role of corticothalamic projections via functional neurostimulation and implantable neuroprotheses under a behavioral paradigm.
II. Coding Properties of the Inferior Colliculus
The inferior colliculus is a major integrative center of the central auditory system, integrating excitatory and inhibitory inputs from lower brain stem nuclei. To understand coding mechanisms of these neurons, we utilize chronic and acute recordings of single unit neural activity to spectral and temporal varying stimuli. Furthermore, synaptic mechanisms of response generation are further elucidated using single and multicompartmental computational models.
III. In-Vitro Slice Electrophysiology
Along with extracellular single unit recordings, we also utilize brain-slice recordings to understand cellular properties of auditory neurons. These studies encompass both electrical and optical stimulation modalities.
In collaboration with the Garner lab at Purdue University, our lab also explores anatomical connections within the central auditory system. We utilize juxtacellular recording in vivo in order to link cell anatomy with functional properties.