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Biomedical subjects

R C Martin

Publications and source records attributed to R C Martin.

At least 19 recordsLinked to original sources
PubMed1992

Enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate and guanosine 3',5' cyclic monophosphate in biological fluids.

Simple, rapid and sensitive competitive enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate (cAMP) and guanosine 3',5' cyclic monophosphate (cGMP) in human plasma and urine are described. Specific antisera to each nucleotide were raised in rabbits by immunization with succinyl cyclic nucleotide--human serum albumin conjugates. For the assay, specific antibodies were incubated with a mixture of succinyl cyclic nucleotide labelled with horseradish peroxidase together with unlabelled standard or sample. The antibody-bound enzyme conjugate was separated from free hapten by anti-rabbit (IgG) sera immobilized to a microtitre plate. Activity of the bound enzyme conjugate was determined with tetramethylbenzidine. The assays were capable of detecting levels as low as 2 fmol of cAMP and cGMP. Good correlations were obtained between values generated by enzyme immunoassay and radioimmunoassay.

Animals↗
PubMed1992

How semantic is automatic semantic priming?

Priming for semantically related concepts was investigated using a lexical decision task designed to reveal automatic semantic priming. Two experiments provided further evidence that priming in a single presentation lexical decision task (McNamara & Altarriba, 1988) derives from automatic processes. Mediated priming, but no inhibition or backward priming was found in this type of lexical decision task. Experiments 3 and 4 demonstrated that automatic priming was found only for associated word pairs, as determined by word association norms, and not for word pairs that are semantically related but not associated. It is argued that automatic priming in the lexical decision task occurs at a lexical level not at a semantic level.

Adult↗
PubMed1991

Hippocampal contribution to verbal recent memory following dominant-hemisphere temporal lobectomy.

The effects of hippocampal encroachment in the language dominant-hemisphere were studied in 41 patients who underwent previous temporal lobectomy (TL). Patients undergoing dominant-hemisphere TL including anterior hippocampus (n = 13) performed significantly worse than nondominant TL patients (n = 16) on a verbal learning test (Selective Reminding; p less than or equal to .00001), thereby confirming the sensitivity of this procedure to lateralized temporal-lobe dysfunction. However, no significant difference was present on this or other primary measures of material-specific memory when contrasting dominant TL patients in whom the anterior hippocampus was spared (n = 12) to those in whom anterior hippocampus was resected. These data suggest that more extensive and posterior mesial temporal-lobe resection is not necessarily associated with a greater verbal material-specific memory deficit following dominant-hemisphere temporal lobectomy.

Adult↗
PubMed1991

Differential effects of unilateral temporal lobectomy on visuospatial memory and attention.

We investigated free recall of visuospatial arrays in a free-field format in epileptic patients following unilateral temporal lobectomy (TL) (left = 15, right = 17). TL patients exhibited leftward deviation in right hemispace, but more variable response in left hemispace, a pattern that has been observed in healthy adults. This finding is postulated to result from combined preferential right cerebral activation and a tendency to err toward peri-personal space. Temporal lobectomy affected overall leftward deviation by initially shifting deviation more toward the side of lesion. The initial directional shift in immediate memory dissipated over time suggesting that these subtle attentional shifts may be compensated by learning. Consistent with differential cerebral hemispheric mechanisms, absolute vertical errors were greater in right than left TL patients, and absolute horizontal errors were worse in right hemispace.

Adult↗
PubMed1990

The effects of lateralized temporal lobe dysfunction on formal and semantic word fluency.

Word fluency performance was studied in 32 patients with unilateral temporal lobe epilepsy (TLE) and 25 healthy dextral controls. Two word fluency tasks were administered conforming to either formal-based criteria or semantic-based criteria. Performance for TLE patients was assessed both pre-operatively and approximately 1 week following anterior temporal lobectomy. Both formal and semantic word fluency decreased regardless of resection laterality. Left TLE patients performed significantly worse at both pre- and post-operative assessments compared to the right TLE patients, while right TLE patients performed significantly poorer than controls on all verbal fluency criteria at pre- and post-operative assessments. In addition, both TLE and control groups produced significantly fewer formal and semantic words during the second 30-sec portion of each task. These findings are discussed in terms of temporal lobe contributions to word fluency production and lexical semantic processing.

Adult↗
PubMed1990

The consequences of reduced memory span for the comprehension of semantic versus syntactic information.

Aphasic patients with restricted memory spans were assessed on their comprehension of syntactically simple sentences varying in numbers of content words and on their comprehension of sentences matched in content words but varying in syntactic complexity. Three different presentation modes were used: unlimited visual presentation, limited visual presentation, and auditory presentation. The difference between performance in the unlimited and limited modes was used as a measure of the extent to which memory decrements caused comprehension failure. These difference scores were related to memory span in order to assess whether the memory involved in sentence processing overlaps that assessed by a memory span task. For the sentences varying in number of content words, performance was worse for the limited presentation modes than the unlimited mode, and the difference between unlimited and limited presentation modes was highly related to memory span. For the sentences varying in syntactic complexity, there was no clear reduction in performance for limited presentation modes, and the difference scores did not relate to memory span. The results support the view that the processing of sentences with many content words draws on the short-term memory capacity assessed by memory span, while the processing of syntactic complexity does not.

Aged↗
PubMed1990

The contribution of an imagery code to verbal memory.

Free recall for auditorially presented spatial information was examined in a patient with a large right cerebral infarction. Despite normal verbal memory at immediate and 30-minute conditions, the patient exhibited a significant loss in verbal recall at 24 hours and a more severe deficit in the recall of the spatial components of prose passages across all delayed recall conditions. These results suggest that although the verbal code is important early in the learning process, spatial imagery exerts an increasing influence over time. Thus, reliance upon a left hemispheric mediated verbal encoding process may only allow for partial integration of linguistic and visuospatial properties.

Adult↗
PubMed1990

The intracarotid amobarbital procedure as a predictor of memory failure following unilateral temporal lobectomy.

We investigated the efficacy of the intracarotid amobarbital procedure to accurately predict post-temporal lobectomy anterograde amnesia. We presented items at 2 separate times during amobarbital assessment; both early and late item recall were decreased during the injection contralateral to seizure onset indicating sensitivity to bilateral temporal lobe dysfunction. Ten patients for whom follow-up neuropsychological assessment was available failed either the early or late item recognition portions of their amobarbital evaluation ipsilateral to seizure onset, but had hippocampus included in the temporal lobectomy by virtue of satisfactory performance on other tests of hippocampal function. None of these 10 patients displayed postoperative anterograde amnesia, although there was a reduction in material-specific memory in some patients. These results indicate that relying solely on amobarbital memory testing to assess the functional ability of the contralateral temporal lobe to sustain global memory prior to temporal lobectomy may needlessly exclude patients from a viable therapeutic option.

Amnesia↗
PubMed1990

Anterograde memory for visuospatial arrays.

A new test was developed to assess direction of errors and hemispatial differences in anterograde memory for visuospatial arrays of abstract figures. After a series of learning trials, delayed recall of figure placement was obtained in 12 healthy dextral adults. Horizontal and vertical errors were measured for each figure. Mean directional error and mean absolute error were calculated for each subject in left and right hemispace for horizontal and vertical dimensions. Although no hemispatial effect was found for mean absolute error, hemispatial differences were present for mean directional error in both horizontal and vertical dimensions. Overall, horizontal deviations were medial, and vertical deviations were downward. However, these effects reached statistical significance only in right hemispace. The directional errors are believed to be due to an attentional shift toward proximal peripersonal space, in combination with attentional shifts from differential left/right cerebral activation.

Adult↗
PubMed1990

Evaluation of adult aphasics with the Pediatric Speech Intelligibility test.

Results of conventional adult speech audiometry may be compromised by the presence of speech/language disorders, such as aphasia. The purpose of this project was to determine the efficacy of the speech intelligibility materials and techniques developed for young children in evaluating central auditory function in aphasic adults. Eight adult aphasics were evaluated with the Pediatric Speech Intelligibility (PSI) test, a picture-pointing approach that was carefully developed to be relatively insensitive to linguistic-cognitive skills and relatively sensitive to auditory-perceptual function. Results on message-to-competition ratio (MCR) functions or performance-intensity (PI) functions were abnormal in all subjects. Most subjects served as their own controls, showing normal performance on one ear coupled with abnormal performance on the other ear. The patterns of abnormalities were consistent with the patterns seen (1) on conventional speech audiometry in brain-lesioned adults without aphasia and (2) on the PSI test in brain-lesioned children without aphasia. An exception to this general observation was an atypical pattern of abnormality on PI-function testing in the subgroup of nonfluent aphasics. The nonfluent subjects showed substantially poorer word-max scores than sentence-max scores, a pattern seen previously in only one other patient group, namely young children with recurrent otitis media. The unusually depressed word-max abnormality was not meaningfully related to clinical diagnostic data regarding the degree of hearing loss and the location and severity of the lesions or to experimental data regarding the integrity of phonologic processing abilities. The observations of ear-specific and condition-specific abnormalities suggest that the linguistically- and cognitively-simplified PSI test may be useful in the evaluation of auditory-specific deficits in the aphasic adult.

Adult↗
PubMed1989

Syntactic loss versus processing deficit: an assessment of two theories of agrammatism and syntactic comprehension deficits.

This research evaluated Grodzinsky's (1984, 1986a) syntactic loss and Kolk and van Grunsven's (1985) working memory impairment explanations of syntactic comprehension deficits in agrammatic aphasics. Four aphasic patients were evaluated who showed different patterns of impairment on morphological and structural aspects of production. The comprehension tasks compared performance on full and truncated passive sentences. The syntactic loss hypothesis predicted worse performance on truncated than full passives, while the working memory deficit hypothesis predicted the reverse. Neither hypothesis was supported, as the patients performed at a similar level on both types of passives. In addition, there was little relation between the patients' production indices and their comprehension level. The results argue against any global theory of agrammatism that attempts to attribute all agrammatic speech and co-occurring syntactic comprehension deficits to the same source.

Aged↗
PubMed1989

Distinguishing auditory and speech-specific perceptual deficits.

The ability to discriminate speech and nonspeech auditory stimuli was tested in a learning disabled child. The perception of speech stimuli was normal when the stimuli were presented in quiet but below normal when the stimuli were presented in noise. Although the perception of pure tone stimuli and environmental sounds was normal both in quiet and noise, the perception of nonspeech stimuli with rapid changes in acoustic information was impaired in noise. These findings illustrate the importance of relating performance for speech and complex nonspeech stimuli in investigating the basis of speech perceptual deficits. Whereas abnormal performance for speech stimuli coupled with normal performance for complex nonspeech stimuli argues for the existence of specialized speech processing mechanisms, abnormal performance for both types of stimuli, as was found in the present subject, argues for the existence of more generalized auditory processing mechanisms.

Adolescent↗
PubMed1988

A developmental study of the auditory Stroop effect.

A pediatric auditory version of the Stroop procedure was developed and administered to 48 normal children from 3 to 6 years of age. Our purpose was to define the developmental course characterizing interaction between auditory and semantic speech dimensions in young children. The procedure was a reaction time (RT) task that required children to respond as quickly and as accurately as possible to words spoken by a male or a female voice. Children were instructed to ignore what was said and to push the "Mommy" button if Mommy was talking or the "Daddy" button if Daddy was talking. Performance was obtained for words with neutral, congruent, and conflicting semantic content. Preschool children manifested processing dependencies that were similar to those observed in adults on the visual Stroop procedure. Conflict between semantic and auditory dimensions significantly increased RT and congruence between the two dimensions significantly decreased RT relative to the neutral condition. The pattern of results indicated that the meaning of words was processed automatically in the normal children. The magnitude of the Stroop effect reflected developmental change with increasing age.

Attention↗
PubMed1987

Articulatory and phonological deficits in short-term memory and their relation to syntactic processing.

The relationships between sentence comprehension deficits and deficits in the articulatory or phonological components of short-term memory were investigated. Nonfluent agrammatic patients showed very poor comprehension of syntax while a group of nonfluent patients who were not agrammatic showed good comprehension, despite both groups showing similar degrees of deficits in an articulatory component of memory. The results imply that a disruption of inner rehearsal has little consequence for auditory sentence comprehension, and that the syntactic comprehension deficits of the agrammatic patients could not be attributed to their memory deficit. A patient with a disruption in phonological storage showed good comprehension for many sentences, but was impaired when a difficult syntactic structure was encountered early in a sentence. It was proposed that phonological storage serves to hold words in a phonological form when sentence processing cannot keep pace with sentence input. Although a role for phonological storage was postulated, the impressive degree of syntactic processing that could be carried out by patients with very restricted memory spans implies that there is little overlap between the memory systems disrupted in these patients and the working memory system presumed to be involved in sentence comprehension.

Adult↗
PubMed1987

Specific auditory perceptual dysfunction in a learning disabled child.

An 11 1/2 year old child with learning disability was evaluated with a battery of auditory and linguistic test procedures: electrophysiologic (auditory brain stem, middle latency response, and late potentials), electroacoustic (stapedial reflexes), and behavioral (measures of phonetic-phonologic, syntactic, and semantic processing). The overall pattern of results suggested the presence of an isolated auditory-phonologic processing disorder. Results supported an auditory-perceptual, as opposed to a linguistic-cognitive, model of learning disability.

Aptitude↗
PubMed1986

Evidence of syntactic deficits in a fluent aphasic.

The syntactic abilities of a mild Wernicke's aphasic were examined in production and comprehension tasks. The patient made few errors involving the omission or substitution of substantives or grammatical markers, especially after the first few weeks of testing. Despite his good ability to produce sentences with acceptable surface form, he continued to make role reversal errors and to produce a restricted range of syntactic forms. In comprehension, he also demonstrated an impairment in his ability to use the syntactic information in a sentence to assign role relations. These syntactic impairments could not be attributed to a short-term memory deficit as the patient showed only a slightly reduced short-term memory span, and showed evidence of having a normal phonological store. Implications for theories of aphasic deficits as well as for theories of normal language processing are discussed.

Aphasia↗