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1.  Studying Temporal Properties of Stimulus-Evoked Responses in the Ventral Nerve Cord of Insects 
Students in undergraduate laboratory settings learn many of the foundational principles of sensory processing in the comparatively simple, easy to study invertebrate nervous system. In this example preparation, the American cockroach, students record action potentials from the fibers in the ventral nerve cord (VNC) that participate in a well explained escape behavior in response to stimulation of its cerci, a pair of mechanosensitive abdominal appendages. A system that allows good control over the time and amplitude of the air pulse delivered to the cerci is described. This experimental setup enables students to extract and display temporal information from recordings to learn how to interpret those responses in the context of the properties of the stimulus. I offer examples of specific investigations and analyses that work well for this purpose in an undergraduate laboratory.
PMCID: PMC3852873  PMID: 24319393
electrophysiology; cerci; giant fibers; interspike interval; autocorrelation; adaptation; phase locking
2.  The Multiple Functions of T Stellate/Multipolar/Chopper Cells in the Ventral Cochlear Nucleus 
Hearing research  2010;276(1-2):61-69.
Acoustic information is brought to the brain by auditory nerve fibers, all of which terminate in the cochlear nuclei, and is passed up the auditory pathway through the principal cells of the cochlear nuclei. A population of neurons variously known as T stellate, type I multipolar, planar multipolar, or chopper cells forms one of the major ascending auditory pathways through the brain stem. T Stellate cells are sharply tuned; as a population they encode the spectrum of sounds. In these neurons, phasic excitation from the auditory nerve is made more tonic by feed forward excitation, coactivation of inhibitory with excitatory inputs, relatively large excitatory currents through NMDA receptors, and relatively little synaptic depression. The mechanisms that make firing tonic also obscure the fine structure of sounds that is represented in the excitatory inputs from the auditory nerve and account for the characteristic chopping response patterns with which T stellate cells respond to tones. In contrast with other principal cells of the ventral cochlear nucleus (VCN), T stellate cells lack a low-voltage-activated potassium conductance and are therefore sensitive to small, steady, neuromodulating currents. The presence of cholinergic, serotonergic and noradrenergic receptors allows the excitability of these cells to be modulated by medial olivocochlear efferent neurons and by neuronal circuits associated with arousal. T Stellate cells deliver acoustic information to the ipsilateral dorsal cochlear nucleus (DCN), ventral nucleus of the trapezoid body (VNTB), periolivary regions around the lateral superior olivary nucleus (LSO), and to the contralateral ventral lemniscal nuclei (VNLL) and inferior colliculus (IC). It is likely that T stellate cells participate in feedback loops through both medial and lateral olivocochlear efferent neurons and they may be a source of ipsilateral excitation of the LSO.
PMCID: PMC3078527  PMID: 21056098
ventral cochlear nucleus; brainstem auditory pathways; ion channels; patch-clamp recording
3.  Responses to Sounds in the Central Auditory System of the Frog: An Advanced Electrophysiology Laboratory in Sensory Processing 
Frogs rely upon vocal communication to advertise for potential mates, to defend territory and to alarm neighbors of danger. Cells in the auditory midbrain of an awake frog display tuning to the spectral energy present in calls based upon discharge rate and encode the temporal properties of calls in the timing of their discharges. This laboratory experiment is designed to allow students to explore the relationship between stimulus amplitude or frequency and response rate, and how the timing of responses can also be used to encode behaviorally relevant features of the stimulus. Action potentials in the midbrain auditory nucleus, the torus semicularis, are evoked by delivery of free field sounds and recorded. Most cells are broadly tuned to frequency, yet some can be fairly precise in preserving periodic structure. The use of a comparative model of study should help students understand principles common among all sensory systems, and an appreciation that the architecture of each system is adaptively matched to the ethological task at hand.
PMCID: PMC3592626  PMID: 23493471
Rana; sensory coding; comparative model; undergraduate neuroscience

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