auditory cortex: Responses to frequency-modulated stimuli in the cat's posterior auditory field. Heil, P & Irvine, D. J Neurophysiol, 79(6):3041-59, 1998.
abstract   bibtex   
The mammalian auditory cortex contains multiple fields but their functional role is poorly understood. Here we examine the responses of single neurons in the posterior auditory field (P) of barbiturate- and ketamine-anesthetized cats to frequency-modulated (FM) sweeps. FM sweeps traversed the excitatory response area of the neuron under study, and FM direction and the linear rate of change of frequency (RCF) were varied systematically. In some neurons, sweeps of different sound pressure levels (SPLs) also were tested. The response magnitude (number of spikes corrected for spontaneous activity) of nearly all field P neurons varied with RCF. RCF response functions displayed a variety of shapes, but most functions were of low-pass characteristic or peaked at rather low RCFs (<100 kHz/s). Neurons with strong responses to high RCFs (high-pass or nonselective RCF response function characteristics) all displayed spike count-SPL functions to tone burst onsets that were monotonic or weakly nonmonotonic. RCF response functions and best RCFs often changed with SPL. For most neurons, FM directional sensitivity, quantified by a directional sensitivity (DS) index, also varied with RCF and SPL, but the mean and width of the distribution of DS indices across all neurons was independent of RCF. Analysis of response timing revealed that the phasic response of a neuron is triggered when the instantaneous frequency of the sweep reaches a particular value, the effective Fi. For a given neuron, values of effective Fi were independent of RCF, but depended on FM direction and SPL and were associated closely with the boundaries of the neuron's frequency versus amplitude response area. The standard deviation (SD) of the latency of the first spike of the response decreased with RCF. When SD was expressed relative to the rate of change of stimulus frequency, the resulting index of frequency jitter increased with RCF and did so rather uniformly in all neurons and largely independent of SPL. These properties suggest that many FM parameters are represented by, and may be encoded in, orderly temporal patterns across different neurons in addition to the strength of responses. When compared with neurons in primary and anterior auditory fields, field P neurons respond better to relatively slow FMs. Together with previous studies of responses to modulations of amplitude, such as tone onsets, our findings suggest more generally that field P may be best suited for processing signals that vary relatively slowly over time.
@Article{Heil1998,
  author   = {P Heil and DR Irvine},
  journal  = {J Neurophysiol},
  title    = {auditory cortex: {R}esponses to frequency-modulated stimuli in the cat's posterior auditory field.},
  year     = {1998},
  number   = {6},
  pages    = {3041-59},
  volume   = {79},
  abstract = {The mammalian auditory cortex contains multiple fields but their functional
	role is poorly understood. Here we examine the responses of single
	neurons in the posterior auditory field (P) of barbiturate- and ketamine-anesthetized
	cats to frequency-modulated (FM) sweeps. FM sweeps traversed the
	excitatory response area of the neuron under study, and FM direction
	and the linear rate of change of frequency (RCF) were varied systematically.
	In some neurons, sweeps of different sound pressure levels (SPLs)
	also were tested. The response magnitude (number of spikes corrected
	for spontaneous activity) of nearly all field P neurons varied with
	RCF. RCF response functions displayed a variety of shapes, but most
	functions were of low-pass characteristic or peaked at rather low
	RCFs (<100 kHz/s). Neurons with strong responses to high RCFs (high-pass
	or nonselective RCF response function characteristics) all displayed
	spike count-SPL functions to tone burst onsets that were monotonic
	or weakly nonmonotonic. RCF response functions and best RCFs often
	changed with SPL. For most neurons, FM directional sensitivity, quantified
	by a directional sensitivity (DS) index, also varied with RCF and
	SPL, but the mean and width of the distribution of DS indices across
	all neurons was independent of RCF. Analysis of response timing revealed
	that the phasic response of a neuron is triggered when the instantaneous
	frequency of the sweep reaches a particular value, the effective
	Fi. For a given neuron, values of effective Fi were independent of
	RCF, but depended on FM direction and SPL and were associated closely
	with the boundaries of the neuron's frequency versus amplitude response
	area. The standard deviation (SD) of the latency of the first spike
	of the response decreased with RCF. When SD was expressed relative
	to the rate of change of stimulus frequency, the resulting index
	of frequency jitter increased with RCF and did so rather uniformly
	in all neurons and largely independent of SPL. These properties suggest
	that many FM parameters are represented by, and may be encoded in,
	orderly temporal patterns across different neurons in addition to
	the strength of responses. When compared with neurons in primary
	and anterior auditory fields, field P neurons respond better to relatively
	slow FMs. Together with previous studies of responses to modulations
	of amplitude, such as tone onsets, our findings suggest more generally
	that field P may be best suited for processing signals that vary
	relatively slowly over time.},
  keywords = {Computing Methodologies, Human, Language, Learning, Mental Processes, Models, Theoretical, Stochastic Processes, Support, U.S. Gov't, Non-P.H.S., Cognition, Linguistics, Neural Networks (Computer), Practice (Psychology), Non-U.S. Gov't, Memory, Psychological, Task Performance and Analysis, Time Factors, Visual Perception, Adult, Attention, Discrimination Learning, Female, Male, Short-Term, Mental Recall, Orientation, Pattern Recognition, Visual, Perceptual Masking, Reading, Concept Formation, Form Perception, Animals, Corpus Striatum, Shrews, P.H.S., Visual Cortex, Visual Pathways, Acoustic Stimulation, Auditory Cortex, Auditory Perception, Cochlea, Ear, Gerbillinae, Glycine, Hearing, Neurons, Space Perception, Strychnine, Adolescent, Decision Making, Reaction Time, Astrocytoma, Brain Mapping, Brain Neoplasms, Cerebral Cortex, Electric Stimulation, Electrophysiology, Epilepsy, Temporal Lobe, Evoked Potentials, Frontal Lobe, Noise, Parietal Lobe, Scalp, Child, Language Development, Psycholinguistics, Brain, Perception, Speech, Vocalization, Animal, Discrimination (Psychology), Hippocampus, Rats, Calcium, Chelating Agents, Excitatory Postsynaptic Potentials, Glutamic Acid, Guanosine Diphosphate, In Vitro, Neuronal Plasticity, Pyramidal Cells, Receptors, AMPA, Metabotropic Glutamate, N-Methyl-D-Aspartate, Somatosensory Cortex, Synapses, Synaptic Transmission, Thionucleotides, Action Potentials, Calcium Channels, L-Type, Electric Conductivity, Entorhinal Cortex, Neurological, Long-Evans, Infant, Mathematics, Statistics, Probability Learning, Problem Solving, Psychophysics, Association Learning, Child Psychology, Habituation (Psychophysiology), Probability Theory, Analysis of Variance, Semantics, Symbolism, Behavior, Eye Movements, Macaca mulatta, Prefrontal Cortex, Cats, Dogs, Haplorhini, Photic Stimulation, Electroencephalography, Nervous System Physiology, Darkness, Grasshoppers, Light, Membrane Potentials, Neural Inhibition, Afferent, Picrotoxin, Vision, Deoxyglucose, Injections, Microspheres, Neural Pathways, Rhodamines, Choice Behavior, Speech Perception, Verbal Learning, Dominance, Cerebral, Fixation, Ocular, Language Tests, Random Allocation, Comparative Study, Saguinus, Sound Spectrography, Species Specificity, Audiometry, Auditory Threshold, Calibration, Data Interpretation, Statistical, Anesthesia, General, Electrodes, Implanted, Pitch Perception, Sound Localization, 9636107},
}

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