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M Merzenich

Publications and source records attributed to M Merzenich.

10 recordsLinked to original sources
PubMed2001

Relations between the neural bases of dynamic auditory processing and phonological processing: evidence from fMRI.

Functional magnetic resonance imaging (fMRI) was used to examine how the brain responds to temporal compression of speech and to determine whether the same regions are also involved in phonological processes associated with reading. Recorded speech was temporally compressed to varying degrees and presented in a sentence verification task. Regions involved in phonological processing were identified in a separate scan using a rhyming judgment task with pseudowords compared to a lettercase judgment task. The left inferior frontal and left superior temporal regions (Broca's and Wernicke's areas), along with the right inferior frontal cortex, demonstrated a convex response to speech compression; their activity increased as compression increased, but then decreased when speech became incomprehensible. Other regions exhibited linear increases in activity as compression increased, including the middle frontal gyri bilaterally. The auditory cortices exhibited compression-related decreases bilaterally, primarily reflecting a decrease in activity when speech became incomprehensible. Rhyme judgments engaged two left inferior frontal gyrus regions (pars triangularis and pars opercularis), of which only the pars triangularis region exhibited significant compression-related activity. These results directly demonstrate that a subset of the left inferior frontal regions involved in phonological processing is also sensitive to transient acoustic features within the range of comprehensible speech.

Adult↗
PubMed1999

A neural network model of temporal code generation and position-invariant pattern recognition.

Numerous studies have suggested that the brain may encode information in the temporal firing pattern of neurons. However, little is known regarding how information may come to be temporally encoded and about the potential computational advantages of temporal coding. Here, it is shown that local inhibition may underlie the temporal encoding of spatial images. As a result of inhibition, the response of a given cell can be significantly modulated by stimulus features outside its own receptive field. Feedforward and lateral inhibition can modulate both the firing rate and temporal features, such as latency. In this article, it is shown that a simple neural network model can use local inhibition to generate temporal codes of handwritten numbers. The temporal encoding of a spatial pattern has the interesting and computationally beneficial feature of exhibiting position invariance. This work demonstrates a manner by which the nervous system may generate temporal codes and shows that temporal encoding can be used to create position-invariant codes.

Nervous System Physiological Phenomena↗
PubMed1998

Language learning impairment: integrating research and remediation.

Timing cues present in the acoustic waveform of speech provide critical information for the recognition and segmentation of the ongoing speech signal. Research has demonstrated that deficient temporal perception rates, that have been shown to specifically disrupt acoustic processing of speech, are related to specific language-based learning impairments (LLI). Temporal processing deficits correlate highly with the phonological discrimination and processing deficits of these children. Electrophysiological single cell mapping studies of sensory cortex in brains of primates have shown that neural circuitry can be remapped after specific, temporally cohesive training regimens, demonstrating the dynamic plasticity of the brain. Recently, we combined these two lines of research in a series of studies that addressed whether the temporal processing deficits seen in LLIs can be significantly modified through adaptive training aimed at reducing temporal integration thresholds. Simultaneously, we developed a computer algorithm that expanded and enhanced the brief, rapidly changing acoustic segments within ongoing speech and used this to provide intensive speech and language training exercises to these children. Results to date from two independent laboratory experiments, as well as a large national clinical efficacy trial, demonstrate that dramatic improvements in temporal integration thresholds, together with speech and language comprehension abilities of LLI children, results from training with these new computer-based training procedures.

Autistic Disorder↗
PubMed1996

Sensory dysfunction associated with repetitive strain injuries of tendinitis and focal hand dystonia: a comparative study.

Repetitive strain injuries are reaching epidemic levels among workers who perform heavy schedules of rapid alternating movements (eg., computer programmers, data entry workers) or repetitive, sustained, coordinated movements (eg., editors, writers, salespeople). The purpose of this study was to determine if patients with repetitive strain injury demonstrated degraded sensory motor performance with their hands. Sixty age-matched adults were recruited, with 15 each assigned to a healthy adult control group, a healthy musician control group, a tendinitis group, or a focal dystonia group. Four sensory motor subtests from the Sensory Integration and Praxis Test were given to the subjects according to a standardized protocol. Using multiple one-factor analyses of variance in the parametric or nonparametric mode followed by post hoc pairwise testing, no significant differences were found between the healthy controls and the musician controls. On the test of kinesthesia, using the left hand, subjects with tendinitis performed significantly worse than controls and subjects with focal dystonia. Compared with controls, subjects with focal dystonia did significantly worse on graphesthesia and manual form perception (part 1 and part 2). Subjects with focal dystonia also did significantly worse than subjects with tendinitis when using the left hand on graphesthesia and manual form perception (part 2). When treating patients with repetitive strain injury, discriminative sensory motor skills must be carefully assessed and may need to be addressed as part of an effective treatment program.

Adult↗
PubMed1979

Origins of the scalp recorded frequency-following response in the cat.

The frequency-following response (FFR) is a short-latency scalp-recorded evoked potential elicited by the presentation of low-frequency acoustic stimuli. It is thought to be the result of the synchronous electrical activity in brain stemauditory nuclei to each wave in the acoustic signal. The present investigation constitutes an attempt to determine the generators of the FFR in the cat by analysis of the response and by section of brain stem auditory nuclei and tracts. Among the results were the following: (1) the cochlear nuclei contribute approximately 50% of the amplitude of the scalp-recordedFFR in the cat. (2) The cochlea also makes a significant contribution, accounting for an average of nearly 25% of the response amplitude. (3) The superior olivary nuclei (and/or the nuclei of the lateral lemnisci) account for about 20% of the response amplitude. (4) The contributions from the inferior colliculi (contrary to earlier studies) were found to be relatively insignificant. (5) As a consequence of the existence of multiple generators, the FFR ample area of hair cell excitation for each stimulus frequency involved in the mediation of the FFR, suggestion that scalp-recorded FFRs could be used to ascertain low-frequency hearingsensitivity in uncooperative human subjects.

Animals↗