Michael P. Rastatter

Vocal Reaction Times to Unilaterally Presented Concrete and Abstract Words: Towards A Theory of Differential Right Hemispheric Semantic Processing

Previous studies investigating hemispheric organization for processing concrete and abstract nouns have provided conflicting results. Using manual reaction time tasks some studies have shown that the right hemisphere is capable of analyzing concrete words but not abstract. Others, however, have inferred that the left hemisphere is the sole analyzer of both types of lexicon. The present study tested these issues further by measuring vocal reaction times of normal subjects to unilaterally presented concrete and abstract items. Results were consistent with a model of functional localization which suggests that the minor hemisphere is capable of differentially processing both types of lexicon in the presence of a dominant left hemisphere.

VOCAL REACTION TIMES TO TACHISTOSCOPICALLY PRESENTED HIGH- AND LOW-FREQUENCY VERBS: SOME EVIDENCE FOR SELECTIVE MINOR HEMISPHERE LINGUISTIC ANALYSIS

The current study investigated the capacity of the right hemisphere to process verbs using a paradigm proven reliable for predicting differential, minor hemisphere lexical analysis in the normal, intact brain. Vocal reaction times of normal subjects were measured to unilaterally presented verbs of high and of low frequency. A significant interaction was noted between the stimulus items and visual fields. Post hoc tests showed that vocal reaction times to verbs of high frequency were significantly faster following right visual-field presentations (right hemisphere). No significant differences in vocal reaction time occurred between the two visual fields for the verbs of low frequency. Also, significant differences were observed between the two types of verbs following left visual-field presentation but not the right. These results were interpreted to suggest that right-hemispheric analysis was restricted to the verbs of high frequency in the presence of a dominant left hemisphere.

Developmental influences on speech-motor equivalence: some implications for articulatory disordered children.

The peak amplitude of EMG activity was measured from the orbicularis oris superior (OOS), orbicularis oris inferior (OOI) and masseter muscles for 3 normal 4-yr.-old children and compared to past data gathered on a group of articulatory disordered children, normal children, and adults. The 4-yr.-olds evidenced greater average peak EMG activity than the other groups, suggesting that speech-sound production becomes more efficient with maturation. Also, levels of variability obtained for the younger children were considerably smaller than for the normal speakers across the three muscles, showing that motor equivalence changes with age whereby the flexibility in the control of articulators increases. The coefficient of variation for the OOI muscle for the disordered children, however, was similar to that for the 4-yr.-olds, while the corresponding data for the other two muscles paralleled those for normal ones. These findings were interpreted as reflecting a delay in the development of speech-motor equivalence that affects certain muscles while sparing others.

HEMISPHERIC SPECIALIZATION FOR PROCESSING CHINESE CHARACTERS: SOME EVIDENCE FROM LEXICAL DECISION VOCAL REACTION TIMES

Lexical decision vocal reaction times (RT) were obtained for a group of Chinese subjects to unilateral tachistoscopically presented pictorial, single, and combination Chinese characters. The RT showed a significant right visual-field advantage, with significant correlations of performance between the visual fields for each type of character. Error analysis gave a significant interaction between visual fields and error type—significantly more false positive errors occurred following left visual-field inputs. These results suggest that the left hemisphere was responsible for processing each type of character, possibly reflecting superior postaccess lexical-decision processes.

Measurements of plasma levels of adrenergic neurotransmitters and primary amino acids in five stuttering subjects: A preliminary report (biochemical aspects of stuttering)

Abstract The present study measured plasma levels of epinephrine, norepinephrine, dopamine, and primary amino acids of five stutters employing state-of-the-art high performance liquid chromatographic technology. Pertinent findings showed that glutamine levels of all five subjects were more than four standard deviation units higher than the reference mean, which was interpreted as reflecting a possible increase in left hemispheric GABAergic activity When considered within the parameters of a reciprocal interhemispheric neurotransmitter balance theory, such findings may well suggest that neurotransmitter ratios between and within the two hemispheres are aberrant in the stuttering population. A theoretical model is presented elucidating these disturbed relationships and their possible influence on speech fluency.

NAMING REACTION TIMES TO TACHISTOSCOPICALLY PRESENTED PICTURES: SOME EVIDENCE OF RIGHT HEMISPHERE ENCODING

The present study measured naming reaction times by normal subjects to unilaterally presented picture stimuli. Significant differences in picture-naming reaction time did not exist between left and right visual-field stimulations. The right hemisphere in the intact brain is capable of generating a verbal label for pictured stimuli. A psychological model suggests that a possible processing synergy between the two hemispheres may be tied to spatial processing and elementary linguistics.

Influence of vocabulary-age on unilateral picture-naming reaction times of normal subjects

The present study measured naming reaction times of normal subjects to unilaterally presented pictures corresponding to vocabulary levels of < 5.5, 9.5–10.5, and >18.0 years of age. An analysis of variance of latencies showed a significant interaction between visual fields and stimuli. Post hoc tests were interpreted to suggest that the normal right hemisphere was capable of performing certain differential picture encoding operations up to 10.5 years of age and not beyond. Also, unlike the left hemisphere, the right hemisphere does not appear to be organized on a developmental hierarchy, which corresponds with the clinical literature.

Identification of time-compressed sentential stimuli by good vs poor readers.

Ability of eight good and eight poor readers (in Grade 1, ages ranging from 6.7 to 7.4 yr.) to discriminate phonemic contrasts presented in 50% time-compressed sentential stimuli (Subtest 13 of the Carrow-Auditory Visual Abilities Test) was measured. Good readers exhibited a significantly higher over-all mean performance than poor readers on the time-compressed task. Effects of time-compression on the perception of manner, place, voicing and frequency contrasts showed a similar pattern of errors for both groups of readers. Implications of the effects of auditory discrimination on reading abilities are discussed.

Reading reaction times of stuttering and nonstuttering subjects to unilaterally presented concrete and abstract words

Abstract The present study was an attempt to investigate further the issues pertaining to cerebral organization for visual language processing in a stuttering and nonstuttering population. Reading reaction times were obtained for a group of 14 stutterers and 14 nonstutterers to unilateral, tachistoscopically presented concrete and abstract words. Results of separate analysis of variance procedures showed that a significant interaction occured between visual fields and stimuli for both groups. In each case, post hoc tests suggested that the left hemisphere proved superior for processing both types of lexicon, with the concrete words being read significantly faster than the abstract items. Additionally, right hemispheric processing was predicted from the data, with reaction times to the abstract words being significantly faster than corresponding values for the concrete items. Such findings suggested that the reciprocal, interhemispheric interactions that account for phonemic recoding asymmetries in the stutterers were similar to those obtained for nonstuttering subjects. It appears that hemispheric asymmetries in the stuttering population are influenced by the processing operation imposed by the experimental task demands.

Fundamental frequency variability in elderly women during production of stressed and unstressed words.

The purpose of this investigation was to examine intrasubject and intersubject fundamental frequency (F0) variability in a group of young adult and elderly female speakers during the production of stressed and unstressed words. While both groups exhibited greater intersubject variability during stressed versus unstressed productions, stressed productions were more variable in the elderly women than in the young adults. Also, the elderly women exhibited greater intrasubject variability during stressed and unstressed productions relative to young adults. Implications of these findings were discussed.