Coding of spatial and temporal information in episodic memory.
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Auditory Perception↗
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Temporal and spatial coding in the rat vibrissal system.
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Animals↗
Stimulus selectivity and its postnatal development in the cat's suprasylvian visual cortex.
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Animals↗
Temporal parameters as cues to phrasal boundaries: a comparison of processing by left- and right-hemisphere brain-damaged individuals.
Two experiments were conducted to examine the ability of left- (LHD) and right-hemisphere-damaged (RHD) patients and normal controls to use temporal cues in rendering phrase grouping decisions. The phrase "pink and black and green" was manipulated to signal a boundary after "pink" or after "black" by altering pre-boundary word durations and pause durations at the boundary in a stepwise fashion. Stimuli were presented to listeners auditorily along with a card with three alternative groupings of colored squares from which to select the presented alternative. Results revealed that normal controls were able to use both temporal cues to identify the intended grouping. In contrast, LHD patients required longer than normal pause durations to consistently identify the intended grouping, suggesting a higher than normal threshold for perception of temporal prosodic cues. Surprisingly, the RHD patients exhibited great difficulty with the task, perhaps due to the limited acoustic cues available in the stimuli.
Aged↗
Some characteristics of tactile channels.
The four information-processing channels of glabrous skin have distinct tuning characteristics which appear to be determined in the periphery at the level of sensory receptors and their afferent nerve fibers. The four-channel model [J Acoust Soc Am 84 (1988) 1680] has been updated to include measurement over a wider frequency range of tuning of the P and NP I channels, psychophysically determined by forward-masking and adaptation tuning curve methods. In addition to differences in their tuning, the P and NP channels differ in the following ways: (1) the P channel, but not NP channels, has been found to be capable of temporal summation, which operates by neural integration; (2) the capacity for spatial summation is also an exclusive property of the P channel; (3) sensitivity declines with age at a greater rate in the P channel than in the NP channels; (4) the masking or adaptation of a channel has no effect on the sensitivity of the other channels, although the channels interact in the summation of the perceived magnitudes of stimuli presented to separate channels.
Acoustic Stimulation↗
A study of neurodevelopmental findings in early adolescent delinquents.
Subtle deficits or delays in the development of the central nervous system in young children are associated with problems affecting learning, behavior, and social adjustment. Less is known about the impact of such neurodevelopmental dysfunction in adolescents. This study assesses the possible association between neurodevelopmental delays and juvenile delinquency. An adolescent neurodevelopment examination was devised and administered to 54 delinquents and 51 secondary school students. Six areas were assessed. There were no significant differences in the prevalence of minor neurologic signs (P = 0.37) or in gross motor function (P = 0.02) and temporal sequential organization (P = 0.04). The greatest differences were in visual processing (P = 0.0002) and auditory-language function (P = 0.0001). Eighteen percent of delinquents and 4% of the comparison group were deficient in two or more neurodevelopmental areas. Nine percent of the delinquents and none of the comparison group had three or more dysfunctions. A neurodevelopmental examination may be a useful diagnostic tool for identifying endogenous factors in behavior, learning, and adjustment problems of this age group. Such findings have implications for the formulation of individualized management strategies.
Adolescent↗
Processing of temporal duration information in working memory after frontodorsal tumour excisions.
This study aimed to test the hypothesis that impairments of temporal duration processing after frontal lobe lesions reflect deficits in executive monitoring functions rather than a domain-specific deficit in the maintenance of duration information in working memory. Patients with frontodorsal lesions, clinical controls with post-central lesions, and healthy controls performed recognition and classification tasks, which should allow for testing maintenance and monitoring functions, respectively. Results showed mild non-selective impairments of the frontal patients on both temporal and spatial recognition tasks, but a marked selective degradation on temporal classification while performance on spatial classification was unimpaired. This suggests that maintenance of duration information in working memory after frontal lesions is basically preserved but that, depending on executive task characteristics, there is a specific deficit in the strategic organization of this type of information.
Adult↗
Discrimination learning of amplitude modulated tones in Mongolian gerbils.
Discrimination learning of 100% sinusoidal amplitude modulated tones (AM) was investigated in adult Mongolian gerbils using a footshock motivated shuttle box avoidance go/no go paradigm. AM stimuli to be discriminated had identical carrier frequency (2 kHz) but differed in modulation frequency (fm) by one octave. Six groups of gerbils were trained to discriminate AM-pairs with fm ranging from 10 to 640 Hz. Learning proceeded faster and discrimination performance was slightly better for low fm, up to 80 Hz, than for high fm, above 80 Hz. These results may be related to cortical AM encoding (Schulze, H. and Langner, G., J. Comp. Physiol. A, 181 (1997) 651-663), which is temporal for low fm (synchrony code) and spatial for high fm (rate-place code). This may implicate different neuronal learning strategies or distinct behavioral meanings influencing the discrimination training.
Acoustic Stimulation↗
The effects of telencephalic pallial lesions on spatial, temporal, and emotional learning in goldfish.
In mammals, the pallial amygdala is implicated in emotional learning and memory, whereas the hippocampus is involved in spatial, contextual, or relational memory. This review presents a set of experiments aimed to study the involvement of the dorsomedial and dorsolateral telencephalon of goldfish in spatial and active avoidance learning. Results showed that (1) medial lesions impaired both acquisition and retention of conditioned avoidance response in two-way active avoidance learning experiments with stimuli overlapping (emotional factor) and with an interstimuli gap (temporal and emotional factors), and (2) the medial lesion did not affect spatial learning (spatial, contextual, or relational factors). In contrast, lateral lesions did not impair conditioned avoidance response with stimuli overlapping, but affected conditioned avoidance response with an interstimuli gap and spatial learning. These results support the presence of two differentiated memory systems in teleost fish based on discrete pallial regions: emotional (dorsomedial telencephalon) and spatial/temporal or relational (dorsolateral telencephalon). Furthermore, these functional data support the homology between the medial pallium of the teleost and the pallial amygdala of land vertebrates, and between the teleost lateral pallium and the mammalian hippocampus.
Amygdala↗
Subcortical neural coding mechanisms for auditory temporal processing.
Biologically relevant sounds such as speech, animal vocalizations and music have distinguishing temporal features that are utilized for effective auditory perception. Common temporal features include sound envelope fluctuations, often modeled in the laboratory by amplitude modulation (AM), and starts and stops in ongoing sounds, which are frequently approximated by hearing researchers as gaps between two sounds or are investigated in forward masking experiments. The auditory system has evolved many neural processing mechanisms for encoding important temporal features of sound. Due to rapid progress made in the field of auditory neuroscience in the past three decades, it is not possible to review all progress in this field in a single article. The goal of the present report is to focus on single-unit mechanisms in the mammalian brainstem auditory system for encoding AM and gaps as illustrative examples of how the system encodes key temporal features of sound. This report, following a systems analysis approach, starts with findings in the auditory nerve and proceeds centrally through the cochlear nucleus, superior olivary complex and inferior colliculus. Some general principles can be seen when reviewing this entire field. For example, as one ascends the central auditory system, a neural encoding shift occurs. An emphasis on synchronous responses for temporal coding exists in the auditory periphery, and more reliance on rate coding occurs as one moves centrally. In addition, for AM, modulation transfer functions become more bandpass as the sound level of the signal is raised, but become more lowpass in shape as background noise is added. In many cases, AM coding can actually increase in the presence of background noise. For gap processing or forward masking, coding for gaps changes from a decrease in spike firing rate for neurons of the peripheral auditory system that have sustained response patterns, to an increase in firing rate for more central neurons with transient responses. Lastly, for gaps and forward masking, as one ascends the auditory system, some suppression effects become quite long (echo suppression), and in some stimulus configurations enhancement to a second sound can take place.
Animals↗
Dissociating neural mechanisms of temporal sequencing and processing phonemes.
Using fMRI, we sought to determine whether the posterior, superior portion of Broca's area performs operations on phoneme segments specifically or implements processes general to sequencing discrete units. Twelve healthy volunteers performed two sequence manipulation tasks and one matching task, using strings of syllables and hummed notes. The posterior portion of Broca's area responded specifically to the sequence manipulation tasks, independent of whether the stimuli were composed of phonemes or hummed notes. In contrast, the left supramarginal gyrus was somewhat more specific to sequencing phoneme segments. These results suggest a functional dissociation of the canonical left hemisphere language regions encompassing the "phonological loop," with the left posterior inferior frontal gyrus responding not to the sound structure of language but rather to sequential operations that may underlie the ability to form words out of dissociable elements.
Acoustic Stimulation↗
Cross-modal perceptual integration of spatially and temporally disparate auditory and visual stimuli.
Under certain conditions, auditory and visual information are integrated into a single unified percept even when they originate in different locations in space. The present study shows how this illusion, known as the ventriloquism effect, depends on spatial, temporal and cognitive factors. A method of psychophysical scaling was employed in combination with simple auditory-visual stimuli (tone bursts and flashing light spots) that were presented with various spatiotemporal disparities. Participants either judged their impression of the likelihood of a common cause (Experiment 1) or spatial alignment (Experiment 2) or synchrony of sound and light (Experiment 3). In all three experiments the participants' judgements depended significantly on temporal disparity whereas influences of spatial disparity were significant in Experiments 1 and 2. Optimum scores were always obtained when auditory stimuli were presented with a delay of 50-100 ms after the visual stimuli. These results demonstrate that both temporal and spatial proximity of the two stimuli are critical for the experience of phenomenal causality. On the other hand, spatio-temporal ranges for optimal perception of phenomenal causality in Experiment 1 were significantly larger than predicted by simultaneous detection of spatial and temporal disparities. This finding suggests that auditory-visual binding was further facilitated by additional, cognitive, factors, associated with the specific instruction to judge the likelihood of a common cause. Obviously, these instructional influences may reflect similar perceptual effects, as have been shown previously by increasing the complexity or cognitive compellingness of auditory-visual stimuli.
Acoustic Stimulation↗
Testing neural network models of memory with behavioral experiments.
In recent years, a number of computational neural networks have been proposed aimed at describing memory functions associated with different subregions of the hippocampus, namely dentate gyrus, CA3 and CA1. Recent evidence suggests that indeed specific subregions of the hippocampus may subserve different computational functions, such as spatial and temporal pattern separation, short-term or working memory, pattern association, and temporal pattern completion.
Animals↗
Nature of motor imitation problems in school-aged males with autism: how congruent are the error types?
This case-comparison study explores the underlying mechanisms of imitation problems in school-aged males with autism. Analysis of congruent error types in their imitation performance was made and compared with appropriate comparisons. Fifty-five males (eight low-functioning with autism: mean age 6y 2mo [SD 7.6mo]; 13 low-functioning with learning disabilities: mean age 6y 3mo [SD 2.8mo]; 17 high-functioning with autism: mean age 8y 9mo [SD 11mo]; and 17 typically developing: mean age 8y 8mo [SD 11.6mo]) were assessed on 18 single gestures and six sequences of hand postures. Imitation performance was videotaped for blind scoring on 21 possible errors by two independent observers. Results revealed that in both groups with autism, imitation required far more effort (more attempts) than in the comparison groups and was less precise (more spatial errors). Typical for low-functioning participants with autism was their less mature imaginary grip in transitive gestures. Typical for high-functioning participants with autism was their preference for immature mirror-image imitations. These observations support the assumption that the underlying mechanisms in motor imitation problems are linked more to the action production system and less to the action conceptual system or to behavioural problems. We postulate that the action production system is delayed rather than deficient.
Autistic Disorder↗
My image of the retina.
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Adaptation, Ocular↗
What memory is for.
Let's start from scratch in thinking about what memory is for, and consequently, how it works. Suppose that memory and conceptualization work in the service of perception and action. In this case, conceptualization is the encoding of patterns of possible physical interaction with a three-dimensional world. These patterns are constrained by the structure of the environment, the structure of our bodies, and memory. Thus, how we perceive and conceive of the environment is determined by the types of bodies we have. Such a memory would not have associations. Instead, how concepts become related (and what it means to be related) is determined by how separate patterns of actions can be combined given the constraints of our bodies. I call this combination "mesh." To avoid hallucination, conceptualization would normally be driven by the environment, and patterns of action from memory would play a supporting, but automatic, role. A significant human skill is learning to suppress the overriding contribution of the environment to conceptualization, thereby allowing memory to guide conceptualization. The effort used in suppressing input from the environment pays off by allowing prediction, recollective memory, and language comprehension. I review theoretical work in cognitive science and empirical work in memory and language comprehension that suggest that it may be possible to investigate connections between topics as disparate as infantile amnesia and mental-model theory.
Cognition↗
Contrast sensitivity in dyslexia.
Contrast sensitivity was determined for dyslexic and normal readers. When testing with temporally ramped (i.e. stimuli with gradual temporal onsets and offsets) gratings of 0.6, 4.0, and 12.0 cycles/deg, we found no difference in contrast sensitivity between dyslexic readers and controls. Using 12.0 cycles/deg gratings with transient (i.e. abrupt) onsets and offsets, we found that dyslexic individuals had, compared to controls, markedly inferior contrast sensitivity at the shortest stimulus durations (i.e. 17, 34, and 102 ms). This deficit may reflect more sluggish temporal summation. There was no difference in sensitivity to 0.6 cycles/deg gratings with transient onsets and offsets. Under these conditions, the two groups showed a consistent and equal increase in sensitivity relative to the ramped baseline condition at 0.6 cycles/deg at the longer stimulus durations. This demonstrates that dyslexic readers have no deficit in their ability to detect stimulus transients, a finding which appears to be inconsistent with a transient system deficit. That detection of the low-frequency stimuli was mediated by the transient system is further indicated by the fact that these stimuli were more susceptible to forward masking than were the high-frequency stimuli. The effects of masking of both high and low spatial-frequency stimuli were about equal for dyslexic readers and controls. This is not in agreement with the transient system deficit theory, according to which one would expect there to be less masking of high spatial-frequency stimuli in the case of dyslexic readers.
Adolescent↗