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Results for “Pattern Recognition, Physiological”

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PubMed2007

Rhyme processing in the brain: an ERP mapping study.

The event-related potential (ERP) N450 component has been described in rhyme detection tasks as a negative response elicited by non-rhyming words in comparison to rhyming ones. This response, which peaked around 450 ms over the midline and right hemisphere recording sites, has been subsequently suggested to start already at approximately 300 ms. Moreover, although, the phonological N450 has first been linked to the semantic N400 component, its cognitive nature and cerebral origin remained debated. In this study, we re-investigated the time course of the electrophysiological responses to rhyming and non-rhyming words and estimated their cerebral generators using source localization methods. Waveform analysis showed that, prior to the N450 response to non-rhyming, a slightly earlier negativity characterized the rhyming condition over left fronto-temporal electrodes and peaked at approximately 350 ms. The analysis of the ERP map series in terms of functional microstates revealed a specific map segment in the rhyming condition and another one in the non-rhyming condition. Source localization indicated that the rhyming-elicited microstate engaged predominantly left frontal and temporal areas while the non rhyming-specific response recruited temporal and parietal regions bilaterally. Our results suggest that, similar to the N400 component that is also induced by mismatch contexts, the N450 might rely on temporal generators.

Adult↗

PubMed2006

Auditory pattern recognition and brief tone discrimination of children with reading disorders.

UNLABELLED: Auditory pattern recognition skills in children with reading disorders were investigated using perceptual tests involving discrimination of frequency and duration tonal patterns. A behavioral test battery involving recognition of the pattern of presentation of tone triads was used in which individual components differed in either frequency or duration. A test involving measurement of difference limens for long and short duration tones was also administered. In comparison to controls, children with reading disorders exhibited significantly higher error rates in discrimination of duration and frequency patterns, as well as larger brief tone frequency difference limens. These results suggest that difficulties in the recognition and processing of auditory patterns may co-occur with decoding deficits in children with reading disorders. LEARNING OUTCOMES: (1) As a result of this activity, the participant will be able to identify a relationship between reading and temporal processing. (2) As a result of this activity, the reader will be able to discuss the difference between sight-word decoding and phonological decoding. (3) As a result of this activity, the reader will be able to explain a relationship between reading skills and the identification of auditory patterns.

Acoustic Stimulation↗

PubMed2005

Children use vowels to help them spell consonants.

English spelling is highly inconsistent in terms of simple sound-to-spelling correspondences but is more consistent when context is taken into account. For example, the choice between ch and tch is determined by the preceding vowel (coach, roach vs. catch, hatch). We investigated children's sensitivity to vowel context when spelling consonants in monosyllabic nonwords. Second graders (7-year-olds) tended to use vowel context correctly when spelling word-final consonants (codas). This use of context was progressively stronger for third and fifth graders as well as for college students. The increase is not due to differences in vocabulary because the contextual patterns are similar in reading materials targeted at all four age groups. Vowel letters (graphotactics) had a stronger influence than did vowel pronunciation. Children also used vowel context when spelling word-initial consonants (onsets); this effect was as strong for second graders as for adults. Thus, novice spellers take advantage of graphotactic information.

Adolescent↗

PubMed2005

The selectivity of canary HVC neurons for the Bird's Own Song: rate coding, temporal coding, or both?

The neuronal selectivity observed in the avian song system for the Bird's Own Song progressively emerged as an extraordinary fruitful model to investigate the neural code underlying the recognition of complex stimuli and the occurrence of learned behaviors. In adult zebra finch, neurons from the HVC (used as a proper name) show very selective auditory responses, firing more to presentation of the Bird's Own Song (BOS) than to reverse BOS or other conspecific songs. However, as adult zebra finches always produce the same stereotyped song, the presence of such highly selective neurons in birds with larger repertoire still remains an open question. Data presented here show that neurons selective for the BOS can be found in adult canary, a seasonal breeding bird which display a large repertoire. More precisely, we found that a large proportion of neurons (29/36) exhibits higher responses to presentation of the forward than to the reverse BOS, and that 22% of the cells were identified as selective on the basis of the d' value. For a cell that was extensively studied, we evaluated to what extent temporal stimulus-related structure predicts the acoustic stimulus using linear or non-linear artificial neural networks (ANN). These analyses indicated that the temporal structure contained in spike trains characterizes more accurately the stimulus than the firing rate. The limitations of applying ANN analyses to electrophysiological data are discussed and potential solutions to increase the confidence in these analysis are proposed.

Action Potentials↗

PubMed2006

Differential aging of the brain: patterns, cognitive correlates and modifiers.

Deciphering the secret of successful aging depends on understanding the patterns and biological underpinnings of cognitive and behavioral changes throughout adulthood. That task is inseparable from comprehending the workings of the brain, the physical substrate of behavior. In this review, we summarize the extant literature on age-related differences and changes in brain structure, including postmortem and noninvasive magnetic resonance imaging (MRI) studies. Among the latter, we survey the evidence from volumetry, diffusion-tensor imaging, and evaluations of white matter hyperintensities (WMH). Further, we review the attempts to elucidate the mechanisms of age-related structural changes by measuring metabolic markers of aging through magnetic resonance spectroscopy (MRS). We discuss the putative links between the pattern of brain aging and the pattern of cognitive decline and stability. We then present examples of activities and conditions (hypertension, hormone deficiency, aerobic fitness) that may influence the course of normal aging in a positive or negative fashion. Lastly, we speculate on several proposed mechanisms of differential brain aging, including neurotransmitter systems, stress and corticosteroids, microvascular changes, calcium homeostasis, and demyelination.

Age Factors↗

PubMed2006

The influence of familiarity on brain activation during haptic exploration of 3-D facemasks.

Little is known about the neural substrates that underlie difficult haptic discrimination of 3-D within-class object stimuli. Recent work [A.R. Kilgour, R. Kitada, P. Servos, T.W. James, S.J. Lederman, Haptic face identification activates ventral occipital and temporal areas: an fMRI study, Brain Cogn. (in press)] suggests that the left fusiform gyrus may contribute to the identification of facemasks that are haptically explored in the absence of vision. Here, we extend this line of research to investigate the influence of familiarity. Subjects were trained extensively to individuate a set of facemasks in the absence of vision using only haptic exploration. Brain activation was then measured using fMRI while subjects performed a haptic face recognition task on familiar and unfamiliar facemasks. A group analysis contrasting familiar and unfamiliar facemasks found that the left fusiform gyrus produced greater activation with familiar facemasks.

Adult↗

PubMed2005

ASR for emotional speech: clarifying the issues and enhancing performance.

There are multiple reasons to expect that recognising the verbal content of emotional speech will be a difficult problem, and recognition rates reported in the literature are in fact low. Including information about prosody improves recognition rate for emotions simulated by actors, but its relevance to the freer patterns of spontaneous speech is unproven. This paper shows that recognition rate for spontaneous emotionally coloured speech can be improved by using a language model based on increased representation of emotional utterances. The models are derived by adapting an already existing corpus, the British National Corpus (BNC). An emotional lexicon is used to identify emotionally coloured words, and sentences containing these words are recombined with the BNC to form a corpus with a raised proportion of emotional material. Using a language model based on that technique improves recognition rate by about 20%.

Emotions↗

PubMed2004

Ensemble dynamics of hippocampal regions CA3 and CA1.

Computational models based on hippocampal connectivity have proposed that CA3 is uniquely positioned as an autoassociative memory network, capable of performing the competing functions of pattern completion and pattern separation. Recently, three independent studies, two using parallel neurophysiological recording methods and one using immediate-early gene imaging, have examined the responses of CA3 and CA1 ensembles to alterations of environmental context in rats. The results provide converging evidence that CA3 is capable of performing nonlinear transformations of sensory input patterns, whereas CA1 may represent changes in input in a more linear fashion.

Animals↗

PubMed2005

Dyslexia and across-hands finger localization deficits.

Two experiments on finger localization are reported. Experiment 1 compared children who were poor readers with two groups of children matched to poor readers for sex and either age (CA controls) or reading age (RA controls). The participant's hands were kept out of his or her sight in a semi-open box while the fingers of one hand were lightly touched by the experimenter. The participant's task was to indicate, using the thumb of either the same hand (within-hand condition) or the opposite hand (across-hands condition) to respond, the finger(s) which had been touched by the experimenter. Performance was significantly impaired in the across-hands condition compared with the within-hand condition. Experiment 2 was carried out with dyslexic adults and a control group of normal readers. Using the same method of responding as in Experiment 1, a significant deficit in the across-hands condition compared to the within-hand condition was found for both groups. The effect was also obtained for both groups when participants were required to point to the relevant fingers on a photograph of a hand rather than use the thumb of the opposite hand to respond. The results are discussed in relation to the hypothesis of a deficit in inter-hemispheric transfer of tactile information in dyslexia.

Adult↗

PubMed2006

Pattern recognition using a device substituting audition for vision in blindfolded sighted subjects.

A major question in the field of sensory substitution concerns the nature of the perception generated by sensory substitution devices. In the present fMRI study, we investigated the neural substrates of pattern recognition through a device substituting audition for vision in blindfolded sighted subjects, before and after a short training period. Before training, pattern recognition recruited dorsal and ventral extra-striate areas. After training, the recruitment of these visual areas was found to have increased. These results suggest that visual imagery processes could be involved in pattern recognition and that perception through the substitution device could be visual-like.

Adult↗

PubMed2004

The role of stimulus ambiguity and movement in spatial navigation: a multiple memory systems analysis of location discrimination.

This paper reviews recent findings about how rats navigate by learning to discriminate among locations. The assumption underlying the experiments and their interpretation is that the information required to do this is learned by three independent, parallel memory systems. One system processes cognitive information (or "knowledge"), a second system processes reinforced stimulus-response associations and a third processes Pavlovian conditioned responses in the form of stimulus-affect associations. The information stored in each system produces behavior that, in some cases, results in a location discrimination. The present experiments focus on three factors that influence what each system learns and whether the resulting memory produces behavior that results in a location discrimination. One factor is whether the locations to be discriminated can be identified by unique, unambiguous stimuli or whether they are ambiguously associated with the same stimuli. The second factor is whether the stimuli are observed passively or whether the rats move among them, voluntarily or involuntarily. The third factor is whether or not the rats perform specific reinforced responses in the presence of the stimuli. Instances of co-operative behavioral outputs from memory systems that facilitate location discriminations and of competitive outputs that impede discriminations are described.

Animals↗

PubMed2004

Something in the way she moves.

A recent study using a crossmodal matching task showed that the identity of a talker could be recognized even when the auditory and visual stimuli that were being matched were different sentences spoken by the talker. This finding implies that general temporal features of a person's speech are shared across the auditory and visual modalities.

Acoustic Stimulation↗

PubMed2006

Nonlinear dynamics and pattern bifurcations in a model for vegetation stripes in semi-arid environments.

In many semi-arid environments, vegetation is self-organised into spatial patterns. The most striking examples of this are on gentle slopes, where striped patterns are typical, running parallel to the contours. Previously, Klausmeier [1999. Regular and irregular patterns in semiarid vegetation. Science 284, 1826-1828.] has proposed a model for vegetation stripes based on competition for water. Here, we present a detailed study of the patterned solutions in the full nonlinear model, using numerical bifurcation analysis of both the pattern odes and the model pdes. We show that patterns exist for a wide range of rainfall levels, and in particular for much lower rainfall than have been considered by previous authors. Moreover, we show that for many rainfall levels, patterns with a variety of different wavelengths are stable, with mode selection dependent on initial conditions. This raises the possibility of hysteresis, and in numerical solutions of the model we show that pattern selection depends on rainfall history in a relatively simple way.

Demography↗

PubMed1999

Visual attention modifies spectral sensitivity of nystagmic eye movements.

If we look out of the window of a travelling train our eyes move rapidly back and forth (saccadic movement). With no attention to individual objects, gaze velocity is low but nystagmic frequency is high (stare nystagmus). If we are interested in individual objects, the angular velocity of gaze is high and the nystagmic frequency low (look nystagmus) (Ter Braak, J.W.G. (1936). Untersuchungen ueber optokinetischen Nystagmus. Archives Néerlandaises de Physiologie de L'homme et des Animaux, 21, 309-376). We show that the spectral sensitivities of the two types of nystagmus differ and that the short-wavelength-sensitive cones significantly contribute only to look nystagmus.

Adaptation, Ocular↗

PubMed2003

Response-monitoring dysfunction in aging and Alzheimer's disease: an event-related potential study.

Executive control is a broad-reaching function that includes response monitoring and is likely implemented in the frontal lobes. Age- and dementia-related changes in response-monitoring were assessed during a Picture-Name Verification Task, using response-synchronized event-related potential (ERP) markers of response monitoring: the centrally oriented error-related negativity (ERN); the smaller and more frontally-oriented correct-response negativity (CRN); and the positivity associated with errors (Pe), a marker of error awareness. These were recorded from 10 younger and 10 older healthy controls, as well as 12 Alzheimer's disease (AD) patients. Although the older and younger controls showed equivalent accuracy, error awareness (Pe), and relative ERN>CRN amplitude, aging was associated with slower behavioral responses and decreased ERN amplitude. Although dementia was associated with decreased accuracy, decreased ERN, and a loss of relative ERN>CRN amplitude, error awareness (Pe) remained somewhat intact in AD patients. In AD patients, CRN amplitude was affected by item certainty (assessed a week earlier), being larger to items that were idiosyncratically difficult for patients to name.

Adult↗

PubMed1990

A new technique for estimating chromatic isoluminance in humans and monkeys.

Current approaches to the problem of equating different colors for luminance (chromatic isoluminance) rely upon human reports of perceptual events that are reduced at some luminance ratio. In this report, a technique is described that evokes a vivid percept of motion of a textured pattern only at isoluminance. Furthermore, in both humans and monkeys, the moving stimulus produces a striking optokinetic response in the same direction as the perceived motion. If used in this manner, the technique can provide an estimate of chromatic isoluminance in a variety of species and be used to corroborate a human subject's perceptual judgement.

Animals↗

PubMed2006

Categorization of sounds.

The authors conducted 4 experiments to test the decision-bound, prototype, and distribution theories for the categorization of sounds. They used as stimuli sounds varying in either resonance frequency or duration. They created different experimental conditions by varying the variance and overlap of 2 stimulus distributions used in a training phase and varying the size of the stimulus continuum used in the subsequent test phase. When resonance frequency was the stimulus dimension, the pattern of categorization-function slopes was in accordance with the decision-bound theory. When duration was the stimulus dimension, however, the slope pattern gave partial support for the decision-bound and distribution theories. The authors introduce a new categorization model combining aspects of decision-bound and distribution theories that gives a superior account of the slope patterns across the 2 stimulus dimensions.

Analysis of Variance↗

PubMed2006

Evidence for tempo-specific timing in music using a web-based experimental setup.

Perceptual invariance has been studied and found in several domains of cognition, including those of speech, motor behavior, and object motion. It has also been the topic of several studies in music perception. However, the existing perceptual studies present rather inconclusive evidence with regard to the perceptual invariance of expressive timing under tempo transformation in music performance. The current study used a novel experimental methodology that took advantage of new technologies, such as an online Internet setup, high-quality audio, and state-of-the-art tempo-transformation techniques. The results show that listeners could detect which was the original performance when asked to compare 2 recordings, 1 of which was tempo-transformed to make both similar in overall tempo. This result is taken as support for the tempo-specific timing hypothesis--which predicts that a tempo-transformed performance will sound less natural than an original performance--and as counterevidence for the relationally invariant timing hypothesis, which predicts that a tempo-transformed performance will sound equally natural.

Auditory Perception↗