Biomedical subjects

Catherine M Warrier

Publications and source records attributed to Catherine M Warrier.

5 recordsLinked to original sources

PubMed2004

Right temporal cortex is critical for utilization of melodic contextual cues in a pitch constancy task.

Pitch constancy, perceiving the same pitch from tones with differing spectral shapes, requires one to extract the fundamental frequency from two sets of harmonics and compare them. We previously showed this difficult task to be easier when tonal context is present, presumably because the context creates a tonal reference point from which to judge the test tone. The present study assessed the role of the right auditory cortex in using tonal context for pitch judgements. Thirty-six patients with focal brain excisions of the right or left anterior temporal lobe (RT, LT) and 12 matched control participants (NC) made pitch judgements on complex tones that could differ in fundamental frequency and/or spectral shape. This task was performed in isolation and within a melodic context. The RT group showed impairments both on trials in which extraction of pitch from differing spectral shapes was required (different-timbre trials) and when this was not required (same-timbre trials). All groups performed poorly in the isolated condition, but improved with melodic context. Degree of improvement varied in that the LT group performed normally, whereas the RT group was not able to obtain the same amount of facilitation from the melodic context. In particular, melodic context did not facilitate the RT group's performance on different-timbre trials. Excisions within Heschl's gyrus did not affect these results, suggesting that the impairments were due to the removal of the anterior temporal cortex. The results of this study therefore implicate right anterior auditory cortical areas in making pitch judgements relative to tones that were heard previously. We propose that auditory association areas located on the anterior portion of the superior temporal gyrus, an area with connections to frontal regions implicated in working memory, could be involved in holding and integrating tonal information.

Adult↗

PubMed2004

Learning impaired children exhibit timing deficits and training-related improvements in auditory cortical responses to speech in noise.

The physiological mechanisms that contribute to abnormal encoding of speech in children with learning problems are yet to be well understood. Furthermore, speech perception problems appear to be particularly exacerbated by background noise in this population. This study compared speech-evoked cortical responses recorded in a noisy background to those recorded in quiet in normal children (NL) and children with learning problems (LP). Timing differences between responses recorded in quiet and in background noise were assessed by cross-correlating the responses with each other. Overall response magnitude was measured with root-mean-square (RMS) amplitude. Cross-correlation scores indicated that 23% of LP children exhibited cortical neural timing abnormalities such that their neurophysiological representation of speech sounds became distorted in the presence of background noise. The latency of the N2 response in noise was isolated as being the root of this distortion. RMS amplitudes in these children did not differ from NL children, indicating that this result was not due to a difference in response magnitude. LP children who participated in a commercial auditory training program and exhibited improved cortical timing also showed improvements in phonological perception. Consequently, auditory pathway timing deficits can be objectively observed in LP children, and auditory training can diminish these deficits.

Acoustic Stimulation↗

PubMed2003

Neural plasticity following auditory training in children with learning problems.

OBJECTIVE: This study examined the plasticity of the central auditory pathway and accompanying cognitive changes in children with learning problems. METHODS: Children diagnosed with a learning disability and/or attention deficit disorder worked with commercial auditory processing training software for 8 weeks; control groups consisted of normal-learning and learning-impaired children who did not participate in any remedial programs. Auditory brainstem function was evaluated in response to click and speech stimuli in quiet; cortical responses to speech stimuli were obtained in quiet and noise. Academic achievement and cognitive abilities were assessed with standardized measures. RESULTS: Compared to controls, the trained group improved on measures of auditory processing and exhibited changes in cortical responses in quiet and in noise. In quiet, cortical responses reflected an accelerated maturational pattern; in background noise, cortical responses became more resistant to degradation. Brainstem responses did not change with training. CONCLUSIONS: Children with learning problems who practiced with auditory training software exhibited plasticity of neural encoding of speech sounds at the cortical, but not subcortical, level of the auditory pathway. This plasticity was accompanied by improvement in behavioral performance. SIGNIFICANCE: This study demonstrates that in learning-impaired children working with commercial auditory processing training programs affects both the perception and the cortical representation of sound.

Achievement↗

PubMed2002

Deficits in auditory brainstem pathway encoding of speech sounds in children with learning problems.

Auditory brainstem responses were recorded in normal children (NL) and children clinically diagnosed with a learning problem (LP). These responses were recorded to both a click stimulus and the formant transition portion of a speech syllable /da/. While no latency differences between the NL and LP populations were seen in responses to the click stimuli, the syllable /da/ did elicit latency differences between these two groups. Deficits in cortical processing of signals in noise were seen for those LP subjects with delayed brainstem responses to the /da/, but not for LPs with normal brainstem measures. Preliminary findings indicate that training may be beneficial to LP subjects with brainstem processing delays.

Acoustic Stimulation↗

PubMed2002

Influence of tonal context and timbral variation on perception of pitch.

In this study, spectral timbre's effect on pitch perception is examined in varying contexts. In two experiments, subjects detected pitch deviations of tones differing in brightness in an isolated context in which they compared two tones, in a tone-series context in which they judged whether the last tone of a simple sequence was in or out of tune, and in a melodic context in which they determined whether the last note of familiar melodies was in or out of tune. Timbre influenced pitch judgments in all the conditions, but increasing tonal context allowed the subjects to extract pitch information more accurately. This appears to be due to two factors: (1) The presence of extra tones creates a stronger reference point from which to judge pitch, and (2) the melodies' tonal structure gives more cues that facilitate pitch extraction, even in the face of conflicting spectral information.

Adult↗