Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Auditory Cortex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2001

Spatial localization after excision of human auditory cortex.

Neurophysiological and animal ablation studies concur that primary auditory cortex is necessary for computation of the spatial coordinates of a sound source. Human studies have reported conflicting findings but have often suffered from inadequate psychophysical measures and/or poor lesion localization. We tested patients with unilateral temporal lobe excisions either encroaching on or sparing Heschl's gyrus (HG), quantifying lesion extent using anatomical magnetic resonance imaging measures. Subjects performed two tasks. In the localization task, they heard single clicks in a free-field spatial array subtending 180 degrees of azimuth and indicated the perceived location with a laser pointer. In the discrimination task, two clicks were presented, and subjects indicated if they were in the same or different position. As a group, patients with right temporal excision, either encroaching onto HG or not, were significantly impaired in both hemifields in both tasks, although this was not true for all individuals. Patients with left temporal resections generally performed normally, although some of the patients with left HG excision showed impaired performance bilaterally, especially in the discrimination task. This pattern stands in marked contrast to previous studies showing significant preservation of localization in hemispherectomized patients. We conclude that (1) contrary to hypotheses derived from animal studies, human auditory spatial processes are dependent primarily on cortical areas within right superior temporal cortex, which encompass both spatial hemifields; (2) functional reorganization may not take place after restricted focal damage but only after more extensive early damage; and (3) the existence of individual differences likely illustrates differential patterns of functional lateralization and/or recovery.

Acoustic Stimulation↗
PubMedDate not supplied

Terminal morphology and distribution of corticothalamic fibers originating from layers 5 and 6 of cat primary auditory cortex.

Two types of terminations were observed on corticothalamic fibers arising from cells in different layers of cat auditory cortex. Injections of the anterograde tracers Phaseolus vulgaris leucoagglutinin (PHA-L) or biocytin were made into single cortical loci that included both superficial layer 5 (5a) and layer 6 in the primary auditory cortex (AI). These resulted in labeling of terminal fibers with small (approximately 1 micron) and large (approximately 2 microns) boutons in the medial geniculate complex (MG) and the lateral nucleus of the posterior complex. Large boutons were found in the deep and superficial dorsal nuclei, in the ventrolateral nucleus, and, less frequently, in the medial nucleus of the MG. They usually ended in grape-like clusters of boutons. By contrast, small boutons were found densely in the pars lateralis and pars ovoidea of the ventral nucleus, and to a lesser extent in the medial nucleus of MG. In the anterior third of the ventral nucleus, where the highest density of labeled fibers was observed, the small bouton terminations formed a plate-like plexus. In the inferior colliculus (IC), most terminal boutons on labeled corticotectal fibers were of large size. To reveal the cells of origin of the axons ending in the two different types of corticothalamic terminations, biocytin injections were localized in either layer 5 or layer 6 of AI or PHA-L injections were made into middle layers, including layer 5a but excluding layer 6. Virtually all labeled terminals found in the MG after layer 5 injections were of large size, while those found after layer 6 injections were of small size. The distribution of terminals of single-labeled axons was extensive and variable. For example, an axon recovered after a layer 5 injection of biocytin ended in at least seven patches of clusters of large boutons along much of the anteroposterior axis of MG. Our previous findings showed two neuronal populations situated in superficial layer 5 and in layer 6 of AI and projecting to the thalamus. The axons of these cells had different patterns of collateral distributions in the cortex. The present study shows that the extrinsically projecting axons of these two populations also have different terminal morphologies and distribution patterns in the MG. The findings suggest that the corticothalamic pathway in the cat auditory system consists of at least two feedback projections originating from different cortical layers that exert different influences on distinct thalamic neuronal populations.

Animals↗
PubMed2000

Spatio-temporal analyses of stimulus-evoked and spontaneous stochastic neural activity observed by optical imaging in guinea pig auditory cortex.

Stimulus-evoked response in the cortex involves random neural activity besides the deterministic responses reproducible to the stimulus. Recently, we have developed a new bright optical system that enables us to investigate the spatio-temporal patterns of such stochastic activity in the guinea pig auditory cortex without averaging. We show that (1) the stochastic neural activity is evoked by a tone-stimulus in addition to the deterministic response, and spontaneous stochastic activity is also observed in a similar manner; (2) our statistical estimation of optical responses such as variance showed that the evoked stochastic activity was increased by the sound stimulus compared to the spontaneous activity; (3) both types of stochastic activity mainly display oscillatory behavior, in the frequency range of 5-11 Hz; (4) there are no significant differences between the stimulus-induced and spontaneous stochastic neural activity in our statistical analyses using the PSD (power-spectrum density) and the spatial correlation function; (5) the spatial area of the evoked stochastic activity is not strongly correlated with the tonotopical area of the deterministic response that is mainly localized in the caudal area of field A of the guinea pig auditory cortex. Thus, the stochastic neural activity existing in the stimulus response and the spontaneous activity in the auditory cortex are possibly generated by a common neural mechanism. These results were confirmed statistically using 27 animals.

Acoustic Stimulation↗
PubMed1998

The influence of stimulus properties, complexity, and contingency on the stability and variability of ongoing and evoked activity in human auditory cortex.

The real-time, single-trial activity in the human auditory cortex was extracted from magnetoencephalographic signals. A predictor of single-trial activity was defined as the sum of the average response and a mean-free base level computed over a range of base times. For simple stimuli the residual (predicted-actual) activity had a stimulus-independent oscillatory (10 Hz) component. This component was larger and more durable in trained subjects, reaching saturation only in the most trained of the five subjects studied (S1). Changes in variability and associated reduction of the absolute value and duration of the oscillations were evident in experiments with stimuli loaded with information, saliency, or task contingency. Repetition reintroduces stimulus-independent oscillations very slowly. For S1, after training, the stimulus-independent oscillations were reestablished in the auditory cortices to the level seen for simple stimuli, except for the time periods and in the hemisphere associated with the combination of task demands and stimulus processing.

Adult↗
PubMed2000

Magnetoencephalographic studies of functional organization and plasticity of the human auditory cortex.

Magnetoencephalography has proven to be a powerful noninvasive tool for investigating the functional organization of the human auditory cortex and its plastic changes. The first part of this review summarizes some recent experiments on the tonotopic organization, which can be observed not only in the slow auditory evoked fields, but also in the middle-latency and the steady-state fields. In the second part of this review, recent studies on plasticity of the auditory cortex are outlined. These studies showed that the cortical representation of tones may change within hours after a reversible "functional deafferentation" (short-term plasticity) and that early musical training leads to an expansion in the cortical representation of complex harmonic sounds (long-term plasticity).

Acoustic Stimulation↗
PubMed1995

Synchrony between single-unit activity and local field potentials in relation to periodicity coding in primary auditory cortex.

1. We recorded responses from 136 single units and the corresponding local field potentials (LFPs) from the same electrode at 44 positions in the primary auditory cortex of 25 juvenile, ketamine-anesthetized cats in response to periodic click trains with click repetition rates between 1 and 32 Hz; to Poisson-distributed click trains with an average click rate of 4 Hz; and under spontaneous conditions. The aim of the study is to evaluate the synchrony between LFPs and single-unit responses, to compare their coding of periodic stimuli, and to elucidate mechanisms that limit this periodicity coding in primary auditory cortex. 2. We obtained averaged LFPs either as click-triggered averages, the classical evoked potentials, or as spike-triggered averages. We quantified LFPs by initial negative peak-to-positive peak amplitude. In addition, we obtained trigger events from negativegoing level crossings (at approximately 2 SD below the mean) of the 100-Hz low-pass electrode signal. We analyzed these LFP triggers similarly to single-unit spikes. 3. The average ratio of the LFP amplitude in response to the second click in a train and the LFP amplitude to the first click as a function of click rate was low-pass with a slight resonance at approximately 10 Hz, and, above that frequency, decreasing with a slope of approximately 24 dB/octave. We found the 50% point at approximately 16 Hz. In contrast, the LFP amplitude averaged over entire click trains was low-pass with a similar resonance but a high-frequency slope of 12 dB/octave and a 50% point at approximately 12 Hz. 4. The LFP amplitude for click repetition rates between 5 and 11 Hz often showed augmentation, i.e., the amplitude increased in response to the first few clicks in the train and thereafter decreased. This augmentation was paralleled by an increase in the probability of firing in single units simultaneously recorded on the same electrode. 5. We calculated temporal modulation transfer functions (tMTFs) for single-unit spikes and for LFP triggers. They were typically bandpass with a best modulating frequency of 10 Hz and similar shape for both single-unit spikes and LFP triggers. The tMTF per click, obtained by dividing the tMTF by the number of clicks in the train, was low-pass with a 50% cutoff frequency at approximately Hz, similar to that for the average LFP amplitude. 6. the close similarity of the tMTFs for single-unit spikes and LFP triggers suggests that single-unit tMTFs can be predicted from LFP level crossings.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1993

Tonotopic and functional organization in the auditory cortex of the big brown bat, Eptesicus fuscus.

1. In Eptesicus the auditory cortex, as defined by electrical activity recorded from microelectrodes in response to tone bursts, FM sweeps, and combinations of FM sweeps, encompasses an average cortical surface area of 5.7 mm2. This area is large with respect to the total cortical surface area and reflects the importance of auditory processing to this species of bat. 2. The predominant pattern of organization in response to tone bursts observed in each cortex is tonotopic, with three discernible divisions revealed by our data. However, although cortical best-frequency (BF) maps from most of the individual bats are similar, no two maps are identical. The largest division contains an average of 84% of the auditory cortical surface area, with BF tonotopically mapped from high to low along the anteroposterior axis and is part of the primary auditory cortex. The medium division encompasses an average of 13% of the auditory cortical surface area, with highly variable BF organization across bats. The third region is the smallest, with an average of only 3% of auditory cortical surface area and is located at the anterolateral edge of the cortex. This region is marked by a reversal of the tonotopic axis and a restriction in the range of BFs as compared with the larger, tonotopically organized division. 3. A population of cortical neurons was found (n = 39) in which each neuron exhibited two BF threshold minima (BF1 and BF2) in response to tone bursts. These neurons thus have multipeaked frequency threshold tuning curves. In Eptesicus the majority of multipeaked frequency-tuned neurons (n = 27) have threshold minima at frequencies that correspond to a harmonic ratio of three-to-one. In contrast, the majority of multipeaked neurons in cats have threshold minima at frequencies in a ratio of three-to-two. A three-to-one harmonic ratio corresponds to the "spectral notches" produced by interference between overlapping echoes from multiple reflective surfaces in complex sonar targets. Behavioral experiments have demonstrated the ability of Eptesicus to use spectral interference notches for perceiving target shape, and this subpopulation of multipeaked frequency-tuned neurons may be involved in coding of spectral notches. 4. The auditory cortex contains delay-tuned neurons that encode target range (n = 99). Most delay-tuned neurons respond poorly to tones or individual FM sweeps and require combinations of FM sweeps. They are combination sensitive and delay tuned.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Neural representations of sinusoidal amplitude and frequency modulations in the primary auditory cortex of awake primates.

We investigated neural coding of sinusoidally modulated tones (sAM and sFM) in the primary auditory cortex (A1) of awake marmoset monkeys, demonstrating that there are systematic cortical representations of embedded temporal features that are based on both average discharge rate and stimulus-synchronized discharge patterns. The rate-representation appears to be coded alongside the stimulus-synchronized discharges, such that the auditory cortex has access to both rate and temporal representations of the stimulus at high and low frequencies, respectively. Furthermore, we showed that individual auditory cortical neurons, as well as populations of neurons, have common features in their responses to both sAM and sFM stimuli. These results may explain the similarities in the perception of sAM and sFM stimuli as well as the different perceptual qualities effected by different modulation frequencies. The main findings include the following. 1) Responses of cortical neurons to sAM and sFM stimuli in awake marmosets were generally much stronger than responses to unmodulated tones. Some neurons responded to sAM or sFM stimuli but not to pure tones. 2) The discharge rate-based modulation transfer function typically had a band-pass shape and was centered at a preferred modulation frequency (rBMF). Population-averaged mean firing rate peaked at 16- to 32-Hz modulation frequency, indicating that the A1 was maximally excited by this frequency range of temporal modulations. 3) Only approximately 60% of recorded units showed statistically significant discharge synchrony to the modulation waveform of sAM or sFM stimuli. The discharge synchrony-based best modulation frequency (tBMF) was typically lower than the rBMF measured from the same neuron. The distribution of rBMF over the population of neurons was approximately one octave higher than the distribution of tBMF. 4) There was a high degree of similarity between cortical responses to sAM and sFM stimuli that was reflected in both discharge rate- or synchrony-based response measures. 5) Inhibition appeared to be a contributing factor in limiting responses at modulation frequencies above the rBMF of a neuron. And 6) neurons with shorter response latencies tended to have higher tBMF and maximum discharge synchrony frequency than those with longer response latencies. rBMF was not significantly correlated with the minimum response latency.

Acoustic Stimulation↗
PubMed2004

Intracortical responses in human and monkey primary auditory cortex support a temporal processing mechanism for encoding of the voice onset time phonetic parameter.

This study tests the hypothesis that temporal response patterns in primary auditory cortex are potentially relevant for voice onset time (VOT) encoding in two related experiments. The first experiment investigates whether temporal responses reflecting VOT are modulated in a way that can account for boundary shifts that occur with changes in first formant (F1) frequency, and by extension, consonant place of articulation. Evoked potentials recorded from Heschl's gyrus in a patient undergoing epilepsy surgery evaluation are examined. Representation of VOT varies in a manner that reflects the spectral composition of the syllables and the underlying tonotopic organization. Activity patterns averaged across extended regions of Heschl's gyrus parallel changes in the subject's perceptual boundaries. The second experiment investigates whether the physiological boundary for detecting the sequence of two acoustic elements parallels the psychoacoustic result of approximately 20 ms. Population responses evoked by two-tone complexes with variable tone onset times (TOTs) in primary auditory cortex of the monkey are examined. Onset responses evoked by both the first and second tones are detected at a TOT separation as short as 20 ms. Overall, parallels between perceptual and physiological results support the relevance of a population-based temporal processing mechanism for VOT encoding.

Animals↗
PubMed2001

Spontaneous and stimulus-evoked intrinsic optical signals in primary auditory cortex of the cat.

Spontaneous and tone-evoked changes in light reflectance were recorded from primary auditory cortex (A1) of anesthetized cats (barbiturate induction, ketamine maintenance). Spontaneous 0.1-Hz oscillations of reflectance of 540- and 690-nm light were recorded in quiet. Stimulation with tone pips evoked localized reflectance decreases at 540 nm in 3/10 cats. The distribution of patches "activated" by tones of different frequencies reflected the known tonotopic organization of auditory cortex. Stimulus-evoked reflectance changes at 690 nm were observed in 9/10 cats but lacked stimulus-dependent topography. In two experiments, stimulus-evoked optical signals at 540 nm were compared with multiunit responses to the same stimuli recorded at multiple sites. A significant correlation (P < 0.05) between magnitude of reflectance decrease and multiunit response strength was evident in only one of five stimulus conditions in each experiment. There was no significant correlation when data were pooled across all stimulus conditions in either experiment. In one experiment, the spatial distribution of activated patches, evident in records of spontaneous activity at 540 nm, was similar to that of patches activated by tonal stimuli. These results suggest that local cerebral blood volume changes reflect the gross tonotopic organization of A1 but are not restricted to the sites of spiking neurons.

Acoustic Stimulation↗
PubMed1976

Proprioceptive effects on evoked responses to sounds in the cat auditory cortex.

With a view to analyse the influence of neck proprioceptors on directional hearing, evoked potentials (EPs) to dichotically or monaurally presented clicks were recorded from the auditory cortex of cats under deep Nembutal anaesthesia with their head pointing to the front, and then to the right or to the left side at 45 degrees. The change in the head position produced considerable changes in the amplitude of the two primary EP components and in their thresholds. The changes were of two kinds: either decrease or increase of the amplitude. At symmetrical points of the auditory cortex they went in the same direction. The also appeared in the associative zone with the same sign. With monaurally presented clicks, the change of the side of stimulation for the most part resulted in a reversal of the sign of the proprioceptive effect. Similar proprioceptive influences were recorded when the clicks were presented not through earphones but in an open acoustic field.

Animals↗
PubMed1997

Real-time imaging of neural activity during binaural interaction in the guinea pig auditory cortex.

Spatio-temporal patterns of binaural interaction in the guinea pig auditory cortex (AC) were observed using optical recording with a 12 x 12 photodiode array and a voltage-sensitive dye. The amplitudes of the sound-induced light signals from the cortex were transformed into sequential two-dimensional images every 0.58 ms. Binaural sound stimuli evoked an excitatory response followed by a strong inhibition, and contralateral stimuli evoked a strong excitatory response followed by a weak inhibition. Ipsilateral sound stimuli evoked a weak response. Binaural stimulation induced two types of ipsilateral inhibition: a fast binaural inhibition which was detected only after the contralateral and ipsilateral responses were subtracted from the binaural responses, and which appeared 12-25 ms after the onset of stimulation, and a slow binaural inhibitory effect which was clearly observed in the binaural responses themselves, appearing 70-95 ms after the onset of stimulation. The fast binaural inhibition was observed in the same area as the contralateral excitatory response. The inhibited area became stronger and more widespread with increasing intensity of ipsilateral stimulation. We did not observe the specialized organization of binaural neurons as electrophysiologically found in the cat AC, in which binaural neurons of the same binaural response type are clustered together and alternate with clusters of other response types.

Acoustic Stimulation↗
PubMed2001

Spectro-temporal response field characterization with dynamic ripples in ferret primary auditory cortex.

To understand the neural representation of broadband, dynamic sounds in primary auditory cortex (AI), we characterize responses using the spectro-temporal response field (STRF). The STRF describes, predicts, and fully characterizes the linear dynamics of neurons in response to sounds with rich spectro-temporal envelopes. It is computed from the responses to elementary "ripples," a family of sounds with drifting sinusoidal spectral envelopes. The collection of responses to all elementary ripples is the spectro-temporal transfer function. The complex spectro-temporal envelope of any broadband, dynamic sound can expressed as the linear sum of individual ripples. Previous experiments using ripples with downward drifting spectra suggested that the transfer function is separable, i.e., it is reducible into a product of purely temporal and purely spectral functions. Here we measure the responses to upward and downward drifting ripples, assuming reparability within each direction, to determine if the total bidirectional transfer function is fully separable. In general, the combined transfer function for two directions is not symmetric, and hence units in AI are not, in general, fully separable. Consequently, many AI units have complex response properties such as sensitivity to direction of motion, though most inseparable units are not strongly directionally selective. We show that for most neurons, the lack of full separability stems from differences between the upward and downward spectral cross-sections but not from the temporal cross-sections; this places strong constraints on the neural inputs of these AI units.

Acoustic Stimulation↗
PubMed1992

Dynamic characteristics of the auditory cortex of guinea pigs observed with multichannel optical recording.

The spatiotemporal characteristics of neural activity in the guinea pig auditory cortex are investigated to determine their importance in neural processing and coding of the complex sounds. A multi-channel optical recording system has been developed for observing the cortical field of the mammalian brain in vivo. Using the voltage-sensitive dye: RH795, optical imaging was used to visualize neural activity in the guinea pig auditory cortex. Experimental results reveal a boomerang-shaped pattern of movement of activated neural cell regions for the evoked response to click as complex sounds. Parallel and sequential neural processing structure was observed. Although the exact frequency selectivities of single cells and tonotopical organization observed using microelectrode were not visible, the similar feature to the microelectrode evidences was imaged by extracting the strongly response field from the optical data.

Acoustic Stimulation↗
PubMed1997

Transient developmental expression of CD15 in the motor and auditory cortex of the mouse.

The distribution of the glycoprotein CD15 (FAL, SSEA-1, Le(x)) in the developing cortex of the mouse has been examined by immunohistochemistry of paraffin sections. The pattern of CD15 immunoreactivity was observed to occur in 4 stages. In the first stage, the presumptive subplate region in the lateral and rostral parts of the developing isocortex was transiently labelled at E12. In the second stage, between E13 and E17, very faint label was found only in the ventricular germinal zone, possibly within radial glial fibres. The third stage began at E18, when transient labelling of several discrete cortical areas was apparent; the motor cortex (from E18 to P3), an area in the temporal lobe (presumptive primary auditory cortex; from E18 to P5.5) and the piriform and entorhinal cortices (from E18 to P3). The final stage began at P2, when a mosaic camouflage pattern of labelling started to appear throughout the developing cortex, particularly in layer I. The distribution of the transient label in the motor cortex during the perinatal period suggests that it may be associated with early events in corticospinal or other projection neuron maturation (apical dendrite growth and differentiation). The labelling in the presumptive auditory cortex (Te1) may also be involved in the differentiation of neurons in the upper cortical plate.

Aging↗
PubMed1993

Plasticity in the frequency representation of primary auditory cortex following discrimination training in adult owl monkeys.

Previous studies have shown that the tonotopic organization of primary auditory cortex is altered subsequent to restricted cochlear lesions (Robertson and Irvine, 1989) and that the topographic reorganization of the primary somatosensory cortex is correlated with changes in the perceptual acuity of the animal (Recanzone et al., 1992a-d). Here we report an increase in the cortical area of representation of a restricted frequency range in primary auditory cortex of adult owl monkeys that is correlated with the animal's performance at a frequency discrimination task. Monkeys trained for several weeks to discriminate small differences in the frequency of sequentially presented tonal stimuli revealed a progressive improvement in performance with training. At the end of the training period, the tonotopic organization of Al was defined by recording multiple-unit responses at 70-258 cortical locations. These responses were compared to those derived from three normal monkeys and from two monkeys that received the same auditory stimuli but that were engaged in a tactile discrimination task. The cortical representation, the sharpness of tuning, and the latency of the response were greater for the behaviorally relevant frequencies of trained monkeys when compared to the same frequencies of control monkeys. The cortical area of representation was the only studied parameter that was correlated with behavioral performance. These results demonstrate that attended natural stimulation can modify the tonotopic organization of Al in the adult primate, and that this alteration is correlated with changes in perceptual acuity.

Acoustic Stimulation↗
PubMed1999

Effects of noradrenaline on frequency tuning of auditory cortex neurons during wakefulness and slow-wave sleep.

This study shows the effects of noradrenaline (NA) on receptive fields of auditory cortex neurons in awake animals; it is the first one to describe the effects of NA on neurons in sensory cortex, in different natural states of vigilance. The frequency receptive field of 250 auditory cortex neurons was determined before, during and after ionophoretic application of NA while recording the state of vigilance of unanaesthetized guinea-pigs. When NA significantly changed the spontaneous activity (85 out of 250 cells), the dominant effect was a decrease (61 out of 85 cells, 72%). When NA significantly changed the evoked activity (107 out of 250 cells), the dominant effect was also a decrease (84 out of 107 cells, 78%). During and after NA application, the signal-to-noise ratio (S/N, i.e. evoked/spontaneous activity) was unchanged, but the selectivity for pure-tone frequencies was enhanced. When the effects occurring in wakefulness and in slow-wave sleep (SWS) were compared, it appeared that the predominantly inhibitory effect of NA on spontaneous and evoked activity was present in both states. The S/N ratio was unchanged and the selectivity was increased in both states. However, during SWS, the percentage of cells inhibited by NA was lower, and the effects on the frequency selectivity were smaller than in wakefulness. In contrast, GABA produced similar inhibitory effects on spontaneous and on evoked activity during wakefulness and SWS. Comparisons with previous data obtained using the same protocol in urethane anaesthetized animals (Manunta & Edeline 1997) indicate that the effects of NA were qualitatively the same. Based on these results, we suggest that any hypothesis concerning the role of NA in cortical plasticity should take into account the fact that the predominantly inhibitory effects of NA lead to decrease the size of the receptive field.

Acoustic Stimulation↗
PubMed2003

Auditory cortex lesions in the rat impair both temporal acuity and noise increment thresholds, revealing a common neural substrate.

Temporal acuity for acoustic transients in rats with bilateral auditory cortex lesions (n = 6) was compared with that of sham-surgery control rats (n = 4), using a standard gap-detection method. A comparison of sensitivity to quiet gaps in noise and dark gaps in light tested for a cross-modal effect of the lesion. The groups were compared also in their sensitivity to noise offset, to noise increments, and to noise pulses presented in quiet. Stimulus detection was assessed with the startle reflex modification procedure, which uses changes in reflex expression caused by stimuli presented immediately before reflex elicitation as the objective evidence for their detection. There were no group differences in sensitivity to noise offset, noise pulses, or dark gaps in light. In contrast, the lesion reduced sensitivity to noise increments and eliminated gap detection. These deficits were maintained for 1 month and only partially recovered 2 months after surgery. The data indicate that the auditory cortex is critically important for temporal acuity in hearing, and suggest that its contribution to gap detection is to enhance the salience of noise increments at the end of the gap.

Acoustic Stimulation↗