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At least 757 records · Page 42Linked to original sources
PubMed2002

A four-channel analysis of the tactile sensitivity of the fingertip: frequency selectivity, spatial summation, and temporal summation.

Thresholds were measured for the detection of vibratory stimuli of variable frequency and duration applied to the index fingertip and thenar eminence through contactors of different sizes. The effects of stimulus frequency could be accounted for by the frequency characteristics of the Pacinian (P), non-Pacinian (NP) I, and NP III channels previously determined for the thenar eminence (Bolanowski et al., J Acoust Soc Am 84: 1680-1694, 1988; Gescheider et al., Somatosens Mot Res 18: 191-201, 2001). The effect of changing stimulus duration was also essentially identical for both sites, demonstrating the same amount of temporal summation in the P channel. Although the effect of changing stimulus frequency and changing stimulus duration did not differ for the two sites, the effect of varying the size of the stimulus was significantly greater for the thenar eminence than for the fingertip. The attenuated amount of spatial summation on the fingertip was interpreted as an indication that the mechanism of spatial summation consists of the operations of both neural integration and probability summation.

Adolescent↗
PubMed2000

Long-term memory for spatial and temporal mental models includes construction processes and model structure.

There is a strong case that people construct and manipulate mental models in working memory but relatively little evidence that mental models are preserved in long-term memory. Instead people may remember an episodic construction trace: a record of the operations used to construct a mental model (Payne, 1993). Experiment 1 investigated memory for determinate spatial descriptions (which describe a single configuration of objects) and indeterminate spatial descriptions (which describe two equally plausible configurations). Recognition performance was impaired when the overlap between the episodic construction trace of a description at learning and at test was disrupted by reordering the sentences within a description. Participants were better at remembering the gist of determinate descriptions than that of indeterminate descriptions. For indeterminate descriptions, provided differences in gist recognition were controlled, participants showed better memory for the original description. Experiment 2 showed a similar pattern of results with temporal descriptions. A third experiment manipulated the similarity between foils in the recognition test and the original descriptions to provide further evidence for both episodic construction trace and remembered mental models. In combination, these results favour a hybrid account of memory for mental models, which includes information about both construction processes and model structure.

Adult↗
PubMed1996

Spatial imagery preserves temporal order.

Line drawings were presented in either a spatial or a nonspatial format. Subjects recalled each of four sets of 24 items in serial order. Amount recalled in the correct serial order and sequencing errors were scored. In Experiment 1 items appeared either in consecutive locations of a matrix or in one central location. Subjects who saw the items in different locations made fewer sequencing errors than those who saw each item in a central location, but serial recall levels for these two conditions did not differ. When items appeared in nonconsecutive locations in Experiment 2, the advantage of the spatial presentation on sequencing errors disappeared. Experiment 3 included conditions in which both the consecutive and nonconsecutive spatial formats were paired with retrieval cues that either did or did not indicate the sequence of locations in which the items had appeared. Spatial imagery aided sequencing when, and only when, the order of locations in which the stimuli appeared could be reconstructed at retrieval.

Cognition↗
PubMed1989

Spatial and temporal contrast sensitivity in hemianopia. A comparative study of the sighted and blind hemifields.

Spatial and temporal contrast sensitivity was measured, under identical test conditions using spatially and temporally localized stimuli, in 4 normally sighted human subjects and in 3 healthy hemianopic subjects whose stable visual field loss exhibited foveal sparing. Testing was undertaken at central fixation and at a variety of eccentric loci along the horizontal meridian of the sighted and perimetrically blind field. In comparison with the normal (control) sensitivities obtained in this study, spatial and temporal sensitivities in the sighted hemifield in subjects with striate cortical lesions were both reduced; in addition, we were unable to demonstrate greater-than-chance performance at any extrafoveal locations in the blind hemifield.

Contrast Sensitivity↗
PubMed1997

Spatial and temporal auditory processing deficits following right hemisphere infarction. A psychophysical study.

Higher auditory function in a patient was investigated following a right hemisphere infarction between the middle and posterior cerebral artery territories involving the insula. The patient complained of lack of musical appreciation and a battery of tests confirmed a dissociated receptive musical deficit in the presence of normal appreciation of environmental sounds and speech. The ability to detect continuous changes in sound frequency in the form of sinusoidal frequency modulation was preserved. There was, however, a deficit in the analysis of rapid temporal sequences of notes which could underlie his musical deficit. This case provides further evidence for the existence of amusia as a distinct form of auditory agnosia, but does not support the hypothesis that bilateral lesions are required to produce such a deficit. Unexpectedly, the patient was also found to have a deficit in the perception of apparent sound-source movement. We suggest that this deficit is analogous to the visual phenomenon of akinetopsia, and is in accord with PET work suggesting involvement of areas outside primary auditory cortex in sound movement perception. A possible common deficit in auditory temporal and spatial 'scene analysis' is discussed.

Acoustic Stimulation↗
PubMed2006

The effect of temporal context on the sustained pitch response in human auditory cortex.

Recent neuroimaging studies have shown that activity in lateral Heschl's gyrus covaries specifically with the strength of musical pitch. Pitch strength is important for the perceptual distinctiveness of an acoustic event, but in complex auditory scenes, the distinctiveness of an event also depends on its context. In this magnetoencephalography study, we evaluate how temporal context influences the sustained pitch response (SPR) in lateral Heschl's gyrus. In 2 sequences of continuously alternating, periodic target intervals and a more irregular baseline interval, the distinctiveness of the target was decreased in 1 of 2 ways--either by increasing the pitch strength of the baseline or by decreasing the pitch strength of the target. The results show that the amplitude of the SPR increases monotonically with the distinctiveness of the target. Moreover, SPR amplitude is greater for the sequence, where the pitch strength of the target is varied, compared with the condition, where the baseline is varied. Two subsequent experiments show that the amplitude of the SPR increases as duty cycle decreases, in a pitch "strength" contrast and in a pitch "value" contrast. These results indicate that the SPR adapts to recent stimulus history, enhancing the response to rare and brief events.

Acoustic Stimulation↗
PubMed1997

Electrophysiological correlates of temporal and spatial information processing.

In order to study the neurophysiological correlates of working memory for different types of information, event-related brain potentials (ERPs) were recorded during a visual spatial and visual as well as auditory duration memory tasks. From stimulus onset to 500 ms ERPs were distinguishable by allocation to visual or auditory modality. From 500 to 2000 ms after stimulus onset, the spatial task generated a parieto-occipital focused negative slow wave, while corresponding ERPs of the temporal task showed a negative slow wave with frontolateral focus. From 1200 to 5500 ms a large positivity was found for the auditory temporal task and for good performers of the visual temporal task. The data suggest a distinction of three processing phases: modality-specific encoding, information-specific encoding and retention in conjunction with modality-specific inhibition processes.

Acoustic Stimulation↗
PubMed1999

Temporal and speech processing deficits in auditory neuropathy.

Auditory neuropathy affects the normal synchronous activity in the auditory nerve, without affecting the amplification function in the inner ear. Patients with auditory neuropathy often complain that they can hear sounds, but cannot understand speech. Here we report psychophysical tests indicating that these patients' poor speech recognition is due to a severe impairment in their temporal processing abilities. We also simulate this temporal processing impairment in normally hearing listeners and produce similar speech recognition deficits. This study demonstrates the importance of neural synchrony for auditory perceptions including speech recognition in humans. The results should contribute to better diagnosis and treatment of auditory neuropathy.

Acoustic Stimulation↗
PubMed2002

Temporal processing and speech recognition in cochlear implant users.

Although the speech recognition performance of cochlear implant patients has steadily improved in recent years, considerable variability remains in implant patient outcomes. Here, we report on a correlation between cochlear implant patients' auditory temporal processing and speech recognition abilities. Modulation detection thresholds were measured as a function of stimulation level; phoneme recognition was also assessed. Results showed marked individual differences in the shape and absolute sensitivity of subjects' modulation threshold functions. Statistical analysis revealed a strong correlation between phoneme recognition scores and subjects' mean modulation thresholds, demonstrating the contribution of temporal processing to implant speech perception. In correlating a basic psychophysical measure to speech performance, these results should contribute toward improved speech processor design and rehabilitation tools for cochlear implant patients.

Acoustic Stimulation↗
PubMed2002

Temporal envelope perception in dyslexic children.

Speech intelligibility depends heavily on the accurate perception of auditory temporal envelope cues, that is the slower amplitude modulations present in the speech waveform. In a previous study, McAnally and Stein demonstrated that dyslexics may show impaired audibility (i.e. detectability) of these envelope cues. In the present psychophysical study, the ability to process temporal envelope cues was further investigated in dyslexic children by measuring detection thresholds of sinusoidal amplitude-modulation (SAM) and discrimination thresholds of SAM depth and SAM rate. Each threshold was measured at slow and fast SAM rates of 4 and 128 Hz, respectively. Overall, SAM thresholds were higher in dyslexics than in controls at both rates. The strongest deficit was observed at 4 Hz in the SAM detection task, but a deficit was also apparent at 128 Hz in the SAM discrimination tasks. Therefore, these results reveal that, in addition to reduced audibility of slow and fast envelope cues, some dyslexic children show poor encoding fidelity for these cues (as measured by the discrimination tasks). Overall, these findings are consistent with Tallal's hypothesis according to which the speech and reading deficits in some dyslexics may be caused by impaired temporal processes.

Acoustic Stimulation↗
PubMed2001

Central auditory plasticity: changes in the N1-P2 complex after speech-sound training.

OBJECTIVE: To determine whether the N1-P2 complex reflects training-induced changes in neural activity associated with improved voice-onset-time (VOT) perception. DESIGN: Auditory cortical evoked potentials N1 and P2 were obtained from 10 normal-hearing young adults in response to two synthetic speech variants of the syllable /ba/. Using a repeated measures design, subjects were tested before and after training both behaviorally and neurophysiologically to determine whether there were training-related changes. In between pre- and post-testing sessions, subjects were trained to distinguish the -20 and -10 msec VOT /ba/ syllables as being different from each other. Two stimulus presentation rates were used during electrophysiologic testing (390 msec and 910 msec interstimulus interval). RESULTS: Before training, subjects perceived both the -20 msec and -10 msec VOT stimuli as /ba/. Through training, subjects learned to identify the -20 msec VOT stimulus as "mba" and -10 msec VOT stimulus as "ba." As subjects learned to correctly identify the difference between the -20 msec and -10 msec VOT syllabi, an increase in N1-P2 peak-to-peak amplitude was observed. The effects of training were most obvious at the slower stimulus presentation rate. CONCLUSIONS: As perception improved, N1-P2 amplitude increased. These changes in waveform morphology are thought to reflect increases in neural synchrony as well as strengthened neural connections associated with improved speech perception. These findings suggest that the N1-P2 complex may have clinical applications as an objective physiologic correlate of speech-sound representation associated with speech-sound training.

Adult↗
PubMed1982

A unifying concept for the neuropsychological organization of children with reading disability.

Normative studies successfully predicting reading failure in 5- and 6-year-old children suggest that if the neuropsychological functions relating to spatial orientation and temporal organization are not age-appropriate, that child will not have normal achievement in the language arts, particularly in reading. This concept unifying the diverse symptoms found in elementary school children with reading failure has been used to develop a test battery predictive of reading failure, valid to 1 to 3% false positives and 10% false negatives. Further, a simple clinical test, the arm Extension Test, suggests that in these children hemisphere specialization for language has not been established.

Auditory Perception↗
PubMed1988

Effects of changes in brain 5-HT activity on indicators of cortical arousal.

Clinical studies on fluoxetine have reported occasional symptoms of increased fatigue in depressed patients. On the other hand, experimental studies in healthy subjects have demonstrated evidence for fluoxetine-induced increases in cortical arousal. The present placebo-controlled study with 24 healthy subjects was designed to answer the following questions: Does fluoxetine increase measures of cortical arousal and decrease feelings of alertness, and does the 5HT2 receptor blocker ritanserin produce inverse effects to fluoxetine? Analyses of covariance revealed the following results: Fluoxetine produced a slight increase, ritanserin a marked decrease in critical flicker fusion frequency. Time perception was slightly improved by both drugs. Self-ratings on alertness and energy were significantly reduced by both fluoxetine and ritanserin as compared to placebo. Effects for fatigue were increased accordingly. Possible underlying neurophysiological mechanisms and specificity of the effects for cortical as opposed to limbic arousal will be discussed.

Adult↗
PubMed2001

Coping in spouses of patients with acute myocardial infarction in the early phase of recovery.

The purpose of this study was (1) to determine the coping strategies employed by spouses of patients with AMI in the early phase of the crisis, (2) to define the role of age, gender, health perception, time since infarction, spouses' fears, and negative life events in the choice of coping strategies applied, and (3) to test the effect of coping strategies on physical and psychological strain. Fifty-seven spouses participated in the study, 47 were female and 10 were male. Data were collected by structured questionnaires, which were distributed to the spouses from 2 weeks-4 months after the patient's AMI. The researchers found that age, negative life event during the last 12 months, time since infarction, and the spouse's fears influenced the choice of strategies. In the early stage of the crisis, positive reappraisal seems to be a strategy that increased physical strain. Spouses' need for social support in the early stage of the crisis is a factor for health care providers to bear in mind. Besides giving information, empathy, and understanding, health care personnel can try to assist spouses in their efforts to reappraise their situation.

Adaptation, Psychological↗