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At least 775 records · Page 43Linked to original sources
PubMed2006

Cochlear implant-mediated perception of music.

PURPOSE OF REVIEW: This paper examines and consolidates recent advances in cochlear implant sound processing from the perspective of music perception, which is increasingly viewed as one of the most difficult of all listening conditions. RECENT FINDINGS: Music is an essentially abstract, complex form of sound composed of multiple layers of sounds that vary in temporal presentation, frequency distribution, and harmonic content. As a result, music perception is perhaps the most challenging aspect of implant-mediated listening. Thus far, implant performance has shown poor performance overall during perception of musical pitches, melodies, and timbre while perception of rhythm is relatively good. Recent advances in implant sound processing strategies, particularly the use of current distribution along adjacent electrodes, have promising early results in terms of improving the number of pitch percepts available to cochlear implant listeners. SUMMARY: Music perception poses auditory challenges that can exceed those of language perception during cochlear implant-mediated listening. These challenges should be emphasized to patients prior to implantation. Although rhythm perception via cochlear implants is reasonably good using simple test paradigms, significant work remains to improve critically important aspects of music perception, including melody and timbre. New implant processing strategies are encouraging and should lead to improved music perception in the near future.

Auditory Perception↗
PubMed2006

Suicide and deliberate self-harm in personality disorders.

PURPOSE OF REVIEW: This article reviews literature published over the period January 2004-May 2005 on suicidal behaviour and self-harm in personality disorders. RECENT FINDINGS: Studies have confirmed that personality disorders and their co-morbidity with other psychiatric conditions are risk factors for both fatal and nonfatal suicidal behaviours, and self-mutilation. Negative life events, childhood sexual abuse, difficulties in social functioning, deficits in future-directed thinking and time perception, as well as familial and neurocognitive factors may be related to increased suicide risk in individuals with borderline and other personality disorders. Findings seem to confirm that suicidality and self-injurious behaviour are efficient DSM-IV diagnostic criteria for borderline personality disorder. Out of several psychosocial and pharmacological interventions for treating suicidality in personality disorders, only one randomized, controlled study has recently been published. Medico-legal concerns related to the clinical management of chronically suicidal patients, including hospitalization and alternative treatment approaches, are also discussed. SUMMARY: Although recent studies have contributed to the theoretical knowledge and clinical practice, there are unsettled questions that should be addressed in the future. More randomized, controlled trials evaluating the efficacy of interventions in suicidal individuals with personality disorders should be conducted. As the majority of studies conducted to date have concentrated on borderline personality disorder and antisocial personality disorder, the prevalence and risk factors for suicidal behaviours and self-mutilation in other personality disorders require further clarification. The introduction of unified nomenclature related to suicidal behaviours and self-mutilation would facilitate comparability of results across studies.

Comorbidity↗
PubMed2003

Mathematical modelling of animate and intentional motion.

Our aim is to enable a machine to observe and interpret the behaviour of others. Mathematical models are employed to describe certain biological motions. The main challenge is to design models that are both tractable and meaningful. In the first part we will describe how computer vision techniques, in particular visual tracking, can be applied to recognize a small vocabulary of human actions in a constrained scenario. Mainly the problems of viewpoint and scale invariance need to be overcome to formalize a general framework. Hence the second part of the article is devoted to the question whether a particular human action should be captured in a single complex model or whether it is more promising to make extensive use of semantic knowledge and a collection of low-level models that encode certain motion primitives. Scene context plays a crucial role if we intend to give a higher-level interpretation rather than a low-level physical description of the observed motion. A semantic knowledge base is used to establish the scene context. This approach consists of three main components: visual analysis, the mapping from vision to language and the search of the semantic database. A small number of robust visual detectors is used to generate a higher-level description of the scene. The approach together with a number of results is presented in the third part of this article.

Computers↗
PubMedDate not supplied

Memory for temporal order of new and familiar spatial location sequences: role of the medial prefrontal cortex.

Rats with medial prefrontal cortex or sham control lesions were tested on an eight-arm radial maze task to examine memory for the temporal order of a variable and a constant sequence of spatial locations as a function of temporal distance. During the study phase of each trial, rats were allowed to visit each of eight arms once in an order that was randomly selected or fixed for that trial. The test phase required the rats to choose which of two arms occurred earlier in the sequence of arms visited during the study phase. The arms selected as test arms varied according to temporal distance (0, 2, 4, or 6) or the number of arms that occurred between the two test arms in the study phase. For the variable sequences based on new information, control rats showed an increasing temporal distance function. Relative to control rats, medial prefrontal cortex-lesioned rats displayed a temporal order memory deficit across all distances. For the constant sequence based on familiar information, control rats performed well across all distances. Relative to controls, the medial prefrontal cortex-lesioned rats displayed a performance deficit. The results support the idea that the medial prefrontal cortex contributes to mnemonic operations associated with temporal order for new and familiar spatial location information.

Analysis of Variance↗
PubMed2004

Dissociating brain regions controlling the temporal and ordinal structure of learned movement sequences.

We used functional magnetic resonance imaging to investigate if different brain regions are controlling the temporal and ordinal structure of movement sequences during performance. Human subjects performed overlearned spatiotemporal sequences of key-presses using the right index finger. Under different conditions, the temporal and the ordinal structure of the sequences were varied systematically in relation to each other, using a factorial design: COMBINED had a rhythm of eight temporal intervals and a serial order of eight keys; TEMPORAL had an eight-interval rhythm produced on one key; ORDINAL had an isochronous rhythm and an eight-key serial order; two control conditions had an isochronous pulse performed on one or two keys, respectively. Brain regions involved in rhythmic and ordinal control of the sequences were revealed by analysing main effect contrasts for the corresponding factors. TEMPORAL and ORDINAL were also compared directly to test for significant differences. A dissociation was found between largely the presupplementary motor area, the right inferior frontal gyrus and precentral sulcus, and the bilateral superior temporal gyri, involved in temporal control, and lateral fronto-parietal areas, the basal ganglia and the cerebellum, which were implicated in ordinal control. The vermis and the superior colliculus were the only regions with an activity increase specifically related to combining long temporal and ordinal sequences. We conclude that humans use different brain networks for temporal and ordinal sequence control, and that the performance of combined sequences activates both networks, the medial cerebellum, and the superior colliculus.

Adolescent↗
PubMed1991

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double-blind placebo-controlled study.

1. Apomorphine (1 and 5 micrograms kg-1) and placebo were given to nine normal volunteers, using a Latin-square design and double-blind procedures. The visual perception of static and moving patterns (static and motion contrast sensitivity) was evaluated before and 15 min after the dose administration. 2. Apomorphine (1 and 5 micrograms kg-1), as compared with placebo, led to a significant overall reduction of the visual perception of movement. This effect was dose-related, and apomorphine (5 micrograms kg-1) induced a more pronounced decrease in the visual perception of movement than apomorphine (1 microgram kg-1). With apomorphine (5 micrograms kg-1), the reduction was more pronounced for low spatial frequencies, and was linearly inversely correlated to the spatial frequency for a temporal frequency of 3 Hz. Finally, no significant effect of apomorphine was observed for sensitivity to static patterns. 3. Several non exclusive hypotheses may be suggested: The effects of apomorphine may result from stimulation of retinal D1- and/or D2-dopaminergic receptors. Apomorphine may increase the surround inhibition of ganglion cells' receptive-fields. This modification of the centre-surround balance may explain the decrease in contrast sensitivity for low spatial frequencies. The specific effects of apomorphine on the visual perception of movement support the hypothesis that apomorphine preferentially affects the magnocellular pathway which mediates sensitivity to moving patterns.

Adult↗
PubMed2005

Regulating hospital use: length of stay, beds and whiteboards.

This paper presents part of a larger study of contemporary nursing practice and the rationalisation of hospital length of stay. Informed by Michel Foucault's work on governmentality, length of hospital stay and the re-engineering of surgical services are examined, not in terms of numerical representations of hospital use, but as part of social and political processes through which certain concepts are made susceptible to measurement and practices are organised. Using data generated through fieldwork in a hospital surgical division this analysis offers understandings of how social practices around length of hospital stay are translated and how they pattern contemporary hospital nursing practice. Nursing practice is explored through the reconstitution of hospital beds and the demands of local administration of hospital length of stay.

Attitude of Health Personnel↗
PubMed2005

Hemispheric asymmetry for spectral and temporal processing in the human antero-lateral auditory belt cortex.

The present study investigates the acoustic basis of the hemispheric asymmetry for the processing of speech and music. Experiments on this question ideally involve stimuli that are perceptually unrelated to speech and music, but contain acoustic characteristics of both. Stimuli in previous studies were derived from speech samples or tonal sequences. Here we introduce a new class of noise-like sound stimuli with no resemblance of speech or music that permit independent parametric variation of spectral and temporal acoustic complexity. Using these stimuli in a functional MRI experiment, we test the hypothesis of a hemispheric asymmetry for the processing of spectral and temporal sound structure by seeking cortical areas in which the blood oxygen level dependent (BOLD) signal covaries with the number of simultaneous spectral components (spectral complexity) or the temporal modulation rate (temporal complexity) of the stimuli. BOLD-responses from the left and right Heschl's gyrus (HG) and part of the right superior temporal gyrus covaried with the spectral parameter, whereas covariation analysis for the temporal parameter highlighted an area on the left superior temporal gyrus. The portion of superior temporal gyrus in which asymmetrical responses are apparent corresponds to the antero-lateral auditory belt cortex, which has been implicated with spectral integration in animal studies. Our results support a similar function of the anterior auditory belt in humans. The findings indicate that asymmetrical processing of complex sounds in the cerebral hemispheres does not depend on semantic, but rather on acoustic stimulus characteristics.

Acoustic Stimulation↗
PubMed1983

Peripheral and central handicap and encoding.

A linear model of information processing led to many experiments on learning difficulties in the subnormal and severely subnormal. It assumes learning can result from a break in the chain of information flow at any point but overlooks compensatory mechanisms common to a developing organism. To compensate for the model's difficulties, we compared blind and deaf children with subnormal and subnormal autistic children (i.e. localized with general cognitive incapacities). Absence of a modality led to alternative encoding strategies, but in certain circumstances they also occurred in the centrally handicapped. Reasons for the similarities and differences are discussed.

Adolescent↗
PubMed1997

Spatial and temporal frequency selectivity of cells in area 21a of the cat.

1. The spatial and temporal response properties of single cells in area 21a of the anaesthetized cat were assessed using drifting sinusoidal gratings presented at the optimum orientation for each cell. 2. Responses to sinusoidal gratings were dominated by an elevation of the mean discharge, with a relatively small modulated component at the temporal frequency of grating drift. The relative modulation ratio for the majority of cells was less than 1, similar to complex cells in the striate cortex. 3. Of those cells responsive to stimulation with sinusoidal gratings, 94% displayed spatial bandpass characteristics. Values derived from spatial frequency tuning curves were: mean optimum spatial frequency, 0.26 cycles deg-1; mean spatial resolution, 0.86 cycles deg-1; mean spatial bandwidth, 1.8 octaves; and mean normalized bandwidth, 1.3. Two cells (6%) displayed spatial low-pass characteristics. 4. Approximately half our sample of cells (44%) displayed temporal low-pass tuning, while 35% displayed temporal bandpass characteristics. The mean optimum temporal frequency of bandpass cells was 3.3 Hz and the mean temporal bandwidth 1.9 octaves. The remaining cells were classified as temporal broadband (17%) and temporal high-pass (4%). 5. We conclude that the dominant functional input to cells with relatively high spatial frequency selectivity and/or temporal low-pass response properties most probably arises from area 17. The responses of the remaining cells may be explained by input from area 17 or 18.

Animals↗
PubMed2001

The temporal representation of the delay of iterated rippled noise in the ventral cochlear nucleus of the guinea-pig.

1. We have examined the temporal discharge patterns of single units from the ventral cochlear nucleus (VCN) of anaesthetized guinea-pigs in response to iterated rippled noise (IRN). The pitch range evoked by the stimuli was from 32 to 1000 Hz. 2. Single units were classified into four groups using existing classification schemes: primary-like (PL), onset (O), sustained chopper (CS) and transient chopper (CT). For all unit types the delay of the IRN stimuli was well represented in the all-order interspike interval histograms (ISIHs). 3. A subset of the onset units (onset-chopper, OC) showed a clear preference for some delays of the IRN in their first-order interval statistics. We describe this delay preference as 'periodicity tuning'. The delay at which the pitch estimate was at its maximum was designated its best periodicity. The range of best periodicities for OC units was 3.75-13 ms (between 77 and 267 Hz). 4. The other unit types also showed enhancement of the first-order interval statistics at the delay of the IRN. The range of best periodicities was 1.4-8.8 ms (113-714 Hz) for the CT group, 2.25-10.8 ms (93-444 Hz) for the CS group and 0.5-4.6 ms (217-2000 Hz) for the PL group. 5. The correlation between the maximum interval enhancement observed in response to the IRN stimuli and the peak in the first-order ISIH in response to white noise was 0.81 for OC units, 0.72 for CS units, 0.44 for CT units and -0.15 for PL units. 6. These results demonstrate that all unit types in the VCN can enhance the representation of the delay of IRN using first-order interspike intervals (ISIs) over a range of periodicities. CS and OC units show the greatest range of best periodicities and they are well-suited to encode the delay of IRN in their first-order ISIs for a wide range of pitches.

Action Potentials↗
PubMed1992

Mismatch negativity in event-related potentials to auditory stimuli as a function of varying interstimulus interval.

The mismatch negativity, isolated as a component of the event-related brain potential elicited by deviant auditory stimuli, was suggested by Näätänen (1984) as an indirect measure of the inferred neuronal representation of standard stimuli. The purpose of the present study was to determine the duration of the neuronal representation by varying the interstimulus intervals of 1, 6, and 10 seconds within experimental blocks. Mismatch negativities were found to be elicited by deviant stimuli (1500-Hz tones, sequential probability 10%) following standard stimuli (1000-Hz tones) with interstimulus intervals of 1, 6, and 10 s as well. The results suggest a duration of neuronal representation of at least 10 s. The within-block variation of interstimulus interval, the rather low temporal probability of deviants, and their large frequency deviance might explain the present results contradicting earlier findings that suggested a shorter duration of that neuronal representation.

Adult↗