Cerebral Specialization & Lateralization Down Syndrome Abstracts
Dev Psychobiol 11;50 (3): 242-250 (2008 Mar)
Weak hand preference in children with Down syndrome is associated with language deficits
University of Hamburg, Biological Psychology and Neuropsychology, Hamburg, Germany
This study explores associations between language ability and hand
preference in children with Down syndrome. Compared to typically
developing children of the same age, children with Down syndrome
showed weaker hand preference, were less consistent in the hand they
used and also less willing to reach to extreme positions in
contralateral space. Within the group of children with Down syndrome,
those who showed a stronger or more consistent hand preference had
better language and memory skills. This association could not be
explained by differences in non-verbal cognitive ability or hearing loss.
Brain Lang 84 (2): 152-69 (2003 Feb)
Cerebral specialization and verbal-motor integration in adults with and without Down syndrome
Welsh TN, Elliott D, Simon DA
Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, Ont, Canada L8S 4K1
Persons with Down syndrome (DS) tend to exhibit an atypical left ear-right hemisphere advantage (LEA) for the perception of speech sounds. In the present study, a recent adaptation of the dichotic listening procedure was employed to examine interhemispheric integration during the performance of a lateralized verbal-motor task. Although adults with DS (n = 13) demonstrated a right ear-left hemisphere advantage in the dichotic-motor task similar to their peers with (n = 14) and without undifferentiated developmental disabilities (n = 14), they showed an LEA in a free recall dichotic listening task. Based on a comparison of the laterality indices obtained from both dichotic listening procedures, it appears that the manifestation of lateral ear advantages in persons DS may dependent on the response requirements of the task.
Neuropsychology 17 (1): 32-8 (2003 Jan)
Dichotic ear advantages in adults with Down's syndrome predict speech production errors
Bunn L, Welsh TN, Simon DA, Howarth K, Elliott D.
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
Intellectually challenged adults, with and without Down's syndrome (DS), pointed to drawings of animals following the dichotic presentation of animal names. Although there were no reliable ear differences between the 2 groups, there was tremendous between-persons variability within the group of participants with DS. Moreover, left-ear advantages in persons with DS were associated with more speech production errors when participants either read or repeated a string of 1 syllable words. This was not true for control participants. The relationship between ear advantage and speech errors in persons with DS could reflect their unique pattern of cerebral specialization and brain development.
Dev Neuropsychol 21 (2): 157-72 (2002)
Speech production errors in adults with and without Down syndrome following verbal, written, and pictorial cues
Bunn L, Simon DA, Welsh TN, Watson C, Elliott D
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
Adults with Down syndrome and adults with developmental delays not related to Down syndrome were asked to read, repeat, and formulate speech from a picture following the presentation of 2- and 4-word and picture sequences. The speech sequences were produced either immediately after stimulus presentation or following a 5-sec response delay. Overall, participants with Down syndrome produced more memory errors than persons without Down syndrome. Participants with Down syndrome also committed more speech production errors than the other participants, but only when they were required to repeat what they had heard, or to formulate speech from pictures. The speech production performance of the two groups was equivalent in the read condition. These results are discussed with reference to Elliott, Weeks, and Elliott's (1987) model of cerebral specialization, and to verbal short-term memory in persons with Down syndrome.
Brain Lang 69 (2): 193-211 (1999 Sep)
Cerebral specialization for speech production in persons with Down syndrome
Heath M, Elliott D
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
The study of cerebral specialization in persons with Down syndrome (DS) has revealed an anomalous pattern of organization. Specifically, dichotic listening studies (e.g., Elliott & Weeks, 1993) have suggested a left ear/right hemisphere dominance for speech perception for persons with DS. In the current investigation, the cerebral dominance for speech production was examined using the mouth asymmetry technique. In right-handed, nonhandicapped subjects, mouth asymmetry methodology has shown that during speech, the right side of the mouth opens sooner and to a larger degree then the left side (Graves, Goodglass, & Landis, 1982). The phenomenon of right mouth asymmetry (RMA) is believed to reflect the direct access that the musculature on the right side of the face has to the left hemisphere's speech production systems. This direct access may facilitate the transfer of innervatory patterns to the muscles on the right side of the face. In the present study, the lateralization for speech production was investigated in 10 right-handed participants with DS and 10 nonhandicapped subjects. A RMA at the initiation and end of speech production occurred for subjects in both groups. Surprisingly, the degree of asymmetry between groups did not differ, suggesting that the lateralization of speech production is similar for persons with and persons without DS. These results support the biological dissociation model (Elliott, Weeks, & Elliott, 1987), which holds that persons with DS display a unique dissociation between speech perception (right hemisphere) and speech production (left hemisphere).
Am J Ment Retard 99 (6): 605-15 (1995 May)
Cerebral specialization for spatial processing in adults with Down syndrome
Elliott D, Pollock BJ, Chua R, Weeks DJ
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
Cerebral specialization for spatial processing in adults with Down syndrome was examined. In the first experiment, both control and right-handed subjects with Down syndrome exhibited no lateral advantage in a dihaptic shape-matching task, whereas left-handed subjects with Down syndrome displayed an expected left-hand advantage. In a visual field dot enumeration task in the second experiment, all groups exhibited left-field superiority. Thus, atypical cerebral organization of function in adults with Down syndrome appears to be confined to speech perception (Elliott & Weeks, 1993).
Brain Cogn 26 (2): 191-5 (1994 Nov)
Anomalous cerebral lateralization and Down syndrome
Elliott D, Weeks DJ, Chua R
Department of Physical Education, McMaster University, Hamilton, Ontario, Canada
Contrary to Bryden, McManus, and Bulman-Fleming's claim, the dichotic listening and handedness literature indicate that persons with Down syndrome exhibit a unique pattern of cerebral specialization. This pattern creates difficulty for any model of laterality that proposes random specialization of function in the absence of a predisposition toward left hemisphere lateralization for language and motor control.
Cortex 29 (1): 103-13 (1993 Mar)
Cerebral specialization for speech perception and movement organization in adults with Down's syndrome
Elliott D, Weeks DJ
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
Adults with Down's syndrome and a group of undifferentiated mentally handicapped persons were examined using a free recall dichotic listening procedure to determine a laterality index for the perception of speech sounds. Subjects also performed both the visual and verbal portions of a standard apraxia battery. As in previous research, subjects with Down's syndrome tended to display a left ear advantage on the dichotic listening test. As well, they performed better on the apraxia battery when movements were cued visually rather than verbally. This verbal-motor disadvantage increased as the left ear dichotic listening advantage became more pronounced. It is argued that the verbal-motor difficulties experienced by persons with Down's syndrome stem from a dissociation of the functional systems responsible for speech perception and movement organization (Elliott and Weeks, 1990).
Cortex 27 (1): 41-7 (1991 Mar)
Cerebral organization for language in Down's syndrome patients
Piccirilli M, D'Alessandro P, Mazzi P, Sciarma T, Testa A
Department of Neurology, University of Perugia, Italy
Language lateralization was assessed with a dual task procedure in 10 male right-handed patients with Down's Syndrome and relatively preserved linguistic skills. Their performance was compared with that of two control groups, with and without mental retardation, matched with Down's Syndrome individuals for sex, handedness and I.Q. Results did not support the hypothesis that mental retardation is related to specific pattern of cerebral lateralization.
J Ment Defic Res 34 (3): 253-60 (1990 Jun)
Speech dysfluency and manual specialization in Down's syndrome
Devenny DA, Silverman WP
Institute for Basic Research in Developmental Disabilities, New York State Office of Mental Retardation and Developmental Disabilities, Staten Island. 10314
The relationship between speech dysfluency and manual lateralization was studied in 31 adults with Down's syndrome. Analysis of speech samples from videotapes indicated that frequency of dysfluency ranged from normal to very severe; 42% of the subjects were stutterers. Manual lateralization was measured by the demonstrated use of five objects (pencil, comb, toothbrush, ball and scissors); 61% of the subjects had a clear right-hand preference, 13% a left-hand preference, and the remaining subjects (39%) were mixed-handed. Increased dysfluency was associated with increased non-right-handedness, and this finding could not be explained by reference to either generalized linguistic or intellectual deficits. Results suggest individual variation in the speech motor control system in adults with Down's syndrome which may be associated with anomalous cerebral dominance.
Am J Ment Retard 92 (3): 263-71 (1987 Nov)
Cerebral specialization in individuals with Down syndrome
Elliott D, Weeks DJ, Elliott CL
McMaster University
Recent research in which investigators examined cerebral specialization in individuals with Down syndrome was reviewed. Although dichotic listening studies seem to indicate that individuals with Down syndrome are more likely than those without Down syndrome to display a left ear/right hemisphere advantage for speech sounds, evidence from other experimental paradigms makes a simple model of reversed cerebral specialization for individuals with Down syndrome untenable. We proposed a model of cerebral specialization that has as its main feature the biological dissociation between speech perception and the production of speech and other complex movements. In light of this feature, possible directions for future research were discussed.
Am J Ment Defic 91 (5): 480-5 (1987 Mar)
Cerebral specialization in young adults with Down syndrome
Elliott D, Edwards JM, Weeks DJ, Lindley S, Carnahan H
Adults with and without Down syndrome performed a rapid unimanual finger-tapping task alone and while sound-shadowing high frequency words. For male subjects, the concurrent speech disrupted right-hand, but not left-hand performance. Females suffered finger-tapping decrements in both hands in the dual-task situation. These results provide no evidence for reverse (right hemisphere) lateralization of speech in individuals with Down syndrome.
Am J Ment Defic 90 (4): 472-5 (1986 Jan)
Lateral asymmetries in finger-tapping by adolescents and young adults with Down syndrome
Elliott D, Weeks DJ, Jones R
Lateral asymmetries in finger-tapping were compared in right-handed adolescents and young adults with and without Down syndrome in order to examine cerebral specialization in the Down syndrome group. Finger-tapping data revealed that subjects with Down syndrome performed more slowly than did control subjects and failed to show a right-hand tapping advantage. Although the latter finding suggests that individuals with Down syndrome are less lateralized for sequential processing, they exhibited the same pattern of tapping variability as did control subjects; i.e., they were more variable when finger-tapping with their left hands.
J Ment Defic Res 29 (2): 197-205 (1985 Jun)
Receptive language processing and ear advantage of Down's syndrome children
Hartley XY
A group of Down's syndrome (DS) children was tested on Part 5 of the Token Test for Children (TTC) and a dichotic listening test (DLT, digits), and their scores were compared with those of a group of retarded children with other conditions (non-DS), matched on PPVT score and CA. It was found that the DS children showed significantly more of a left ear advantage on the DLT than did the non-DS group, and also performed significantly more poorly than the non-DS children on those tasks requiring an understanding of complex syntactical structures, while they showed no such deficit in performing spatial/simultaneous tasks. When the children were redivided into groups comprised of those showing a right ear advantage, or a non right ear advantage, similar differences between the two groups were found, with the children in the right ear advantage group being superior on the syntactical tasks but not on the spatial tasks. The results are discussed in terms of a direct link, in neurologically intact children, between ear advantage and actual receptive language abilities.
Cortex 20 (2): 221-31 (1984 Jun)
Do individuals with Down's syndrome possess right hemisphere language dominance?
Tannock R, Kershner JR, Oliver J
A dichotic digits task with selective listening and attention-switching instructions, was administered to 10 mentally retarded individuals with Down's Syndrome between the ages of 10 and 37 years. Attention was focused on one ear for 20 trials before switching attention to the opposite ear after a 5-minute interval. A majority displayed a right ear-left hemisphere advantage for correct responses, although this advantage failed to reach significance. Comparison of left and right ear intrusion errors when each ear was attended first showed significantly more intrusions from the unattended right ear. No priming effects were found. The results do not support the hemispheric reversed specialization hypothesis. Rather, it is suggested that while Down's Syndrome individuals do possess an inherent left hemisphere advantage for language, such individuals may suffer from a left hemisphere information processing disorder that can produce functional reversals in dichotic listening.
J Ment Defic Res 26 (4): 263-9 (1982 Dec)
Receptive language processing of Down's syndrome children
Hartley XY
A group of Down's syndrome children was tested on the Token Test for Children (Di Simoni, 1978), and their scores were compared with those of a group of retarded children with other conditions, matched on PPVT score and CA, and a group of non-retarded children, matched on PPVT score. It was found that the Down's syndrome children were significantly poorer than the non-Down's syndrome children on those parts of the test requiring sequential or syntactic processing, while they showed no deficits in performing tasks requiring spatial/simultaneous processing. Both groups of retarded children generally performed more poorly than the non-retarded children. The results were discussed in terms of the language development of Down's syndrome children, given a possible right hemisphere dominance for language processing.
Cortex 17 (2): 241-8 (1981 Jul)
Lateralisation of speech stimuli in young Down's Syndrome children
Hartley XY
The auditory processing of linguistic (single-syllable common nouns) stimulation, presented dichotically, was investigated in a group of young (mean CA = 52 months) Down's Syndrome children and 2 groups of nonretarded children, matched on CA. The Down's Syndrome children showed a significant left ear advantage in processing this material, and the nonretarded children the typical right ear advantage. That an advantage should be shown in such chronologically young retarded children is of relevance to the relationship between lateralisation and cognitive development, and the reversed pattern corroborates work with older Down's Syndrome children.
Am J Ment Defic 82 (1): 44-53 (1977 Jul)
Dichotic verbal processing in Down's syndrome children having qualitatively different speech and language skills
Sommers RK, Starkey KL
A dichotic word task was used to contrast the speech-perceptual functioning of two groups of Down's syndrome children having qualitatively different speech and language skills to that of nonretarded subjects. Although the 20 nonretarded subjects showed an average 23% right-ear effect on the task, the average ear effect for 29 Down's syndrome subjects was essentially zero. The pattern of phonemic processing of 15 Down's syndrome subjects having better speech and language resembled that of the nonretarded subjects; however, the pattern of 14 Down's syndrome subjects having poorer speech and language was atypical. Place of articulation and voicing of phonemes appeared frequently to have different affects in the latter group in the determination of which dichotic words were reported. Although the group having better speech and language had slightly higher MAs and IQs than the poorer group, MAs and IQs were not related to ear-preference scores.