Movement-related slow potentials during motor imagery and motor suppression in humans

Electro-encephalograms (EEGs) associated with motor imagery and motor suppression were recorded from motor-related frontal regions in humans. A negative potential was observed both during motor imagery and during NO-GO responses, as well as in movement trials. The negative potentials observed in the motor imagery trials had a similar pattern to those observed in the movement trials, although the potentials were different from those during NO-GO responses. The peak amplitude of the negative potential recorded at FCz was significantly larger than those recorded at F3, F4, C3, and C4 in the imagery task. The peak amplitude of the negative component in movement trials was larger than that in the imagery trials of all recording positions. By contrast, during the GO/NO-GO task, the peak amplitude during NO-GO responses was larger than that during the GO responses at every position. It appears, therefore, that motor imagery and motor suppression are associated with their own specific internal processes which are reflected by specific EEG patterns in motor-related frontal areas.     

Movement-related potentials and control of associated movements

Previous studies have shown a relationship of the readiness potential (RP) preceding a motor act to motor control, as indexed by eye movement (EM). Greater EM and, therefore, less motor control was associated with increased positivity in preresponse RP components. It was hypothesized that these positive components may reflect processes involved in the inhibition of extraneous or associated movement during the performance of a motor act, especially in younger subjects with less motor development. We developed a finger lift task for detecting irrelevant associated movements (AM) from the responding hand and the nonresponding contralateral hand. During each target finger lift, small movements of the other nontarget fingers from the target hand and the contralateral hand were considered movements that should have been inhibited. Trials for each subject were divided into two bins: associated movement (AM) trials which had movement of target plus nontarget fingers, and trials with only target finger movement detected (NAM). Difference waveforms indicated a positive-going shift on trials with discrete target finger movements (NAM). Age and RP positivity at ipsilateral and posterior regions were significantly correlated. We suggest that, on trials on which associated movements are successfully inhibited, the negativity of the RP is confounded by an overlapping slow positivity. The positivity may be related to the effort needed to inhibit associated movements in order to perform a sharper and more discrete response. This relationship is a function of motor control and, indirectly, of age.     

Use of demographic variables to predict full scale IQ: a replication and extension

The evaluation of current level of neuropsychological functioning is handicapped by the lack of validated actuarial methods for estimating premorbid intellectual functioning. The present study cross-validated and attempted to improve the one existing method of using demographic variables in a systematic way to predict WAIS Full Scale IQ (Wilson et al., 1978). A sample of 491 neurologically normal subjects was used. The results generally supported the IQ prediction equation, but did reveal systematic differences in accuracy of prediction and direction of prediction error for IQs in the high and low ranges. Also, a simpler IQ prediction formula that uses only years of education was developed and compared with the 5-variable Wilson et al. formula.     

Use of demographic variables to predict full scale IQ: A replication and extension

Abstract

The evaluation of current level of neuropsychological functioning is handicapped by the lack of validated actuarial methods for estimating premorbid intellectual functioning. The present study cross-validated and attempted to improve the one existing method of using demographic variables in a systematic way to predict WAIS Full Scale IQ (Wilson et al., 1978). A sample of 491 neurologically normal subjects was used. The results generally supported the IQ prediction equation, but did reveal systematic differences in accuracy of prediction and direction of prediction error for IQs in the high and low ranges. Also, a simpler IQ prediction formula that uses only years of education was developed and compared with the 5-variable Wilson et al. formula.     

Movement-related cortical potentials: their relationship to the laterality, complexity and learning of a movement

Movement-related cortical potentials (MRCPs) to self-paced unilateral movements of different laterality, complexity and practice level were recorded from 14 healthy subjects using the EMG onset as the trigger. The amplitudes at certain time points and slopes of linear regression lines fitted to 3 main shifts have been evaluated. In the early phase of MRCP the potential and slope values were symmetrically distributed around the midline maximum, which indicates that this part of MRCP can not originate from the primary motor area, which is in a contralateral relation with the movement, but from secondary motor areas (SMA and premotor areas). The changes in the voltage levels and slopes of this phase due to the changes in laterality, complexity and practice level of the movement show the relation of this activity with the abstract characteristics of the movement. The decrease of voltages and slope values in the later phases of MRCP in the complex task, which is replaced by higher voltages and slopes after a certain learning period was evaluated as a result of inhibition of associative movements via reafferent feedback signals occurring often in the first stages of learning period.     

Correlations between socioeconomic status, IQ and aetiology in mental retardation: a population-based study of Norwegian children

  Background: Mental retardation (MR) (IQ ≤ 70) is one of the most frequent and debilitating neurological handicaps in children. The aetiologies of MR are multiple and to a certain extent related to social class and the degree of MR. However, recent epidemiological data assessing these relationships are scarce. The objective of the present study was therefore to estimate the associations between socioeconomic status (SES), level of IQ, and causative factors in children with MR. Methods: The investigation was designed as a cross-sectional population-based study of Akershus County, outside Norway's capital Oslo. The source population comprised 30 037 children born between 1980 and 1985. Of 178 children aged 8–13 years, 79 had severe MR (SMR) (IQ < 50) and 99 had mild MR (MMR) (IQ 50–70). SES was grouped from I to V according to parental education. Diagnostic work-up regarding aetiology and medical diagnoses was extensive. The aetiology of MR was divided into two main groups: biopathological MR (n = 143), and unspecified MR, meaning MR of unknown aetiology (n = 35). Biopathological MR was further subdivided into four sub-groups: prenatal, perinatal, postnatal and undetermined timing of the damaging event. Results: SES III, IV and V (the lower grades) increased the risk of MMR. In SES IV and V there was an increased risk of unspecified MR, odds ratio 7.0 and 5.6 (95% CI 1.3, 39.0 and 1.1, 30.0) respectively, compared to SES I. IQ in unspecified MR was significantly higher than in the biopathological aetiology sub-groups. Conclusions: The study showed that parents of children with SMR had a higher socioeconomic level than parents of children with MMR. The findings were also consistent with a partial overlap between unspecified MR and the lower end of normal IQ distribution in the general population. Accepted: 19 October 1999     

Unconscious thought reduces intrusion development: A replication and extension

Background and ObjectivesIntrusive images after a traumatic event, a hallmark feature of post-traumatic stress disorder, are suggested to develop because the trauma memory is disorganized and not integrated into autobiographical memory. Unconscious Thought Theory predicts that information can be conceptually organized after a period of unconscious thought (UT), more so than after conscious thought (CT). We aimed to test the hypothesis that UT decreases intrusions and increases conceptual organization in memory.MethodsParticipants were shown a stressful film and were required to perform an UT task, a CT task, or a distraction task. Intrusions of the film, intrusion qualities, and sequence memory were measured afterwards.ResultsWe confirmed our hypothesis that UT (versus CT or mere distraction) leads to fewer intrusions, thereby replicating earlier research. Contrary to prediction, we found no difference between the conditions on sequence memory. In addition, conscious thought appeared to increase intrusion nowness and arousal.LimitationsThe analogue design and healthy participant sample prevent from generalizing results to other populations. Intrusion frequency and qualities were assessed immediately after the film thereby prohibiting us from drawing conclusions about any long-term effects.ConclusionsEngaging in unconscious thought after a stressful film can reduce intrusion frequency. This has potential implications for clinical interventions to prevent initial stress symptoms. The underlying mechanism remains unclear for now and provides an avenue for future research.     

The relative importance of identity status interview components: replication and extension

The present study partially replicates and extends the work of Rogow et al. (1983) in probing the relative importance of Ego Identity Status Interview components for both sexes. Eighty female and sixty male students attending a New Zealand university were given the Ego Identity Status Interview with identity components of occupation, religion, politics, and sex role beliefs presented in counterbalanced order. Subjects were then asked to rank components in order of importance to their sense of identity and additional identity contents were explored through open-ended questions. This investigation revealed few sex differences in terms of number of content areas having a common rating, hit rates between single or paired content areas and overall identity ratings, rank order for importance of identity contents, or reported areas of additional identity concerns. In support of Rogow findings, this study suggests that identity not be viewed as a unitary structure and encourages the reporting of both component and overall identity status ratings to allow a more comprehensive means of researching the identity formation process. In general, the identity status approach provides a useful model for clinical research of ego synthesis in late adolescence.     

Movement-related potentials in the Go/NoGo task: the P3 reflects both cognitive and motor inhibition.

OBJECTIVE: The contribution of movement-related potentials (MRPs) to the Go/NoGo N2 and P3 'inhibitory' effects is controversial. This study examined these components in overt and covert response inhibition tasks. METHODS: Twenty adult participants counted or button-pressed in response to frequent (60%) and rare (20%) Go stimuli in a Go/NoGo task with equiprobable rare (20%) NoGo stimuli. RESULTS: The N2 NoGo effect did not differ between Count and Press responses, but the P3 NoGo effect was amplified during the Press task. Additionally, subtraction of the ERP waveform for Count NoGo from Press NoGo trials revealed a positivity between 200 and 400ms, occurring maximally over the central region, contralateral to the responding hand. This difference wave became significant at 210-260ms, close to the estimated time taken to stop an overt response. CONCLUSIONS: The N2 NoGo effect may reflect a non-motoric stage of inhibition, or recognition of the need for inhibition, while the NoGo P3 may overlap with a positive MRP occurring specifically on trials where overt motor responses must be inhibited. SIGNIFICANCE: The study confirms that the N2 and P3 NoGo effects are not solely due to movement-related potentials, and posits the NoGo P3 as a marker of motor inhibition.     

Quality of Life in healthy old age: relationships with childhood IQ,minor psychological symptoms and optimism

BACKGROUND: The aim of this study was to examine relationships in old age between Quality of Life (QoL), childhood IQ, current cognitive performance and minor psychological symptoms, and to estimate possible contributions to these relationships made by sex, education, socioeconomic deprivation, current living group, sex, and balance and 6m walk time. METHODS: We conducted a follow-up study on 88 community residents without dementia who were survivors of the Aberdeen City 1921 birth cohort. QoL was measured by the Schedule for the Evaluation of Individual QoL-Direct Weighting (SEIQoL-DW), current cognition by MMSE and Raven's Progressive Matrices (RPM), childhood IQ, minor psychological symptoms as assessed by the Hospital Anxiety and Depression Scale (HADS), and optimism by the Life Orientation Test (LOT); we included balance, 6m walk time and demographic data. RESULTS: QoL was better in men than in women. Women reported more anxiety and depression. QoL correlated significantly with current cognition measured by RPM, childhood intelligence, anxiety and depressive symptoms, optimism and balance. The best model to predict QoL relied on childhood intelligence (13.4% of the variance) and was improved by addition of HADS (8.8 %) and LOT (4.8 %). Other variables did not contribute to the prediction of QoL. CONCLUSION: In the absence of dementia, childhood IQ, HADS and LOT explain 26.9% of the variance in QoL as reported by community-resident old people. The direction of association between current anxiety and depressive symptoms and lower QoL is uncertain. Lower childhood IQ may contribute to coping less well with later life. Lower QoL is not an invariable concomitant of mild cognitive decline.     

Handedness and part-whole relationships: a replication

Nebes' 1971 experiment reporting a deficit in the performance of left-handed subjects on a measure of part-whole relationships was replicated, controlling for family history of handedness and for experimenter knowledge of subject handedness. No differences were found for any comparisons. Results are examined in relation to similar failures to replicate, indicating that the arc-circle measure does not reliably discriminate any visual-spatial differences associated with handedness.     

Relation of lead and social factors to IQ of low-SES children: a partial replication

An independent replication of a previous study (Schroeder et al., 1985) of the effects of interactive social environmental factors on the relationship of lead and Stanford-Binet IQ was performed on 75 of 80 low-SES black children screened by county health departments in North Carolina. Children's mean blood lead (PbB) level was 20.8 micrograms/dl (range, 6.3 to 47.4). Multivariate regression analyses showed no significant interactions between PbB and age, sex, maternal IQ, Caldwell home environment score, or SES (Hollingshead Two-Factor Index). There was a highly significant negative relationship between both mean and maximum PbB levels with IQ, p less than .002; that is, IQ decreased linearly as PbB increased. The most accurate and precise regression model included lead, maternal IQ, home environment, and gender.     

IQ, mental age, complexity, and trial blocks and the response latency of retarded and nonretarded children.

The relationship between MA, IQ, complexity, and trial blocks on the processing performance of nonretarded and retarded children was examined. The main effect of trial blocks and an interaction between MA and Complexity were found to be significant. These results supported the conclusion that MA and not IQ is important for information processing.     

Effects of sex, height and age on motor evoked potentials with magnetic stimulation

Magnetic stimulation of the brain and cervical and lumbar spinal roots was performed on 48 healthy subjects in order to investigate the effects of sex, height and age on motor evoked potentials (MEPs). The compound muscle action potentials were recorded from the abductor pollicis brevis and abductor hallucis muscles. The central motor conduction time (CMCT) was measured between the cerebral cortex and the cervical root and also between the cerebral cortex and the lumbar root. A multiple regression analysis was used to determine which of the physical variables, namely sex, height and age, were significant. A significant gender difference was observed in the MEP latencies and CMCT of the leg, but not in those of the hand. Both height and age had a significant effect on the leg MEP latencies with a lesser effect on the hand MEP latencies. The leg CMCT was also significantly influenced by height and age, while the hand CMCT was not. These results thus suggest that physical variables are very important in defining normal MEPs, especially in the lower limbs. Therefore, when we assess motor function in patients with neurological disorders, both the patients and control groups should be matched for sex, height and age distribution. Received: 8 May 1997 Received in revised form: 1 December 1997 Accepted: 31 December 1997     

Affective status in relation to impulsive, motor and motivational symptoms: Personality, development and physical exercise

The contributions of impulsive and risk-taking behaviour in depressive and bipolar disorders, motivational and motor behaviours in anhedonic and substance addictive states, and the factors, particularly distress and trauma, underlying the development of neuropathology in affective status are described from clinical, epidemiological and laboratory perspectives. In order to distinguish one case factor for biopsychological substrates of health, an array of self-reported characteristics, e.g., positive or negative affect, stress or energy, optimism, etc., that may be predictive or counterpredictive for the propensity for physical exercise and activity were analysed using a linear regression in twelve different studies. Several individual characteristics were found to be markedly and significantly predictive of the exercise propensity, i.e., positive affect, energy, health-seeking behaviour and character, while optimism was of lesser, though significant, importance. Several individual characteristics were found to be significantly counterpredictive: expression of BDI- and HAD-depression, major sleep problems and lack/negligence of healthseeking behaviour. The consequences of physical activity and exercise for both affective well-being, cognitive mobility and neurogenesis is noted, particularly with regard to developmental assets for younger individuals. Affective disorder states may be studied through analyses of personal characteristics that unfold predispositions for symptom-profiles and biomarkers derived from properties of dysfunction, such as impulsiveness, temperament dimensions, anhedonia and ’over-sensitivity’, whether interpersonal or to reward.     

The corticospinal system: from development to motor control.

The corticospinal system is the principal motor system for controlling movements that require the greatest skill and flexibility. It is the last motor system to develop. The pattern of termination of corticospinal axons, as they grow into the spinal gray matter, bears little resemblance to the pattern later in development and in maturity. Refinement of corticospinal terminations occurs during a protracted postnatal period and includes both elimination of transient terminations and growth to new targets. This refinement is driven by neural activity in the motor cortical areas and by limb motor experience. Developing corticospinal terminals compete with each other for synaptic space on spinal neurons. More active terminals are more competitive and are able to secure more synaptic space than their less active counterparts. Corticospinal terminals can activate spinal neurons from very early in development. The importance of this early synaptic activity appears to be more for refining corticospinal connections than for transmitting signals to spinal motor circuits for movement control. The motor control functions of the corticospinal system are not expressed until development of connectional specificity with spinal cord neurons, a strong capacity for corticospinal synapses to facilitate spinal motor circuits, and the formation of the cortical motor map.