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Robert Chen

Publications and source records attributed to Robert Chen.

At least 19 recordsLinked to original sources
PubMed2007

Interhemispheric inhibition in distal and proximal arm representations in the primary motor cortex.

Interhemispheric inhibitory interactions (IHI) operate between homologous distal hand representations in primary motor cortex (M1). It is not known whether proximal arm representations exhibit comparable effects on their homologous counterparts. We studied IHI in different arm representations, targeting triceps brachii (TB, n = 13), first dorsal interosseous (FDI, n = 13), and biceps brachii (BB, n = 7) muscles in healthy volunteers. Transcranial magnetic stimulation test stimuli (TS) were delivered to M1 contralateral to the target muscle preceded 10 ms by a conditioning stimulus (CS) to the opposite M1 at 110-150% resting motor threshold (RMT). IHI was calculated as the ratio between motor-evoked potential (MEP) amplitudes in conditioned relative to unconditioned trials. Mean RMTs were 38.9, 46.9, and 46.0% of stimulator output in FDI, TB, and BB muscles, respectively. IHI was 0.45 +/- 0.41 (FDI), 0.78 +/- 0.38 (TB), and 0.52 +/- 0.32 (BB, P < 0.01) when test MEP amplitudes were matched and 0.28 +/- 0.17 (FDI) and 0.85 +/- 0.31 (TB, P < 0.05) when TS intensities expressed as percentage RMT were matched. Significant IHI (P < 0.05) was identified with minimal CS intensities (expressed as percentage stimulator output) in the 30 s for FDI, 60 s for TB, and 40 s for BB. Additionally, a CS of roughly 120% RMT suppressed the test MEP but not a test H-reflex in BB, suggesting IHI observed in BB is likely mediated by a supraspinal mechanism. We conclude that IHI differs between different arm muscle representations, comparable between BB and FDI but lesser for TB. This finding suggests the amount of IHI between different arm representations does not strictly follow a proximal-to-distal gradient, but may be related to the role of each muscle in functional movement synergies.

Adult↗
PubMed2006

Saccade-related potentials recorded from human subthalamic nucleus.

OBJECTIVE: To investigate an ocular motor role for the STN in Parkinson's disease (PD) patients. METHODS: Potentials were recorded from deep brain stimulation (DBS) electrodes implanted in the vicinity of STN in five PD patients, while patients simultaneously performed visually cued saccades, self-paced saccades and in two patients self-paced wrist extensions. RESULTS: Premovement potentials related to visually cued saccades were found in 4/5 patients and 56% (5/9) of potentials showed phase reversal indicating a local generator. Onsets of these potentials began closer to saccade initiation from STN contacts (0.88+/-0.30s) than thalamic ones (1.39+/-0.28 s). Self-paced saccade-related potentials were found in 4/4 patients. Self-paced saccade potential onsets (1.82+/-0.88 s) were not different from self-paced wrist extension onsets (1.27+/-0.98 s), suggesting a non-specific mechanism could be responsible for both potentials. 50% (3/6) of potentials to self-paced saccades and 66% (2/3) of potentials to self-paced wrist extensions showed phase reversal. Potentials could be found either ipsilaterally or contralaterally with respect to saccade direction. CONCLUSIONS: These subcortical premovement potentials to saccades are similar to Bereitschaftspotentials and contingent negative variations to limb movements recorded in cortical and subcortical regions. SIGNIFICANCE: These studies further support a role of STN in ocular motor control and suggest a common mechanism of motor preparation for both eye and limb movements in the basal ganglia.

Adult↗
PubMed2006

The effects of repetitive transcranial magnetic stimulation on cortical inhibition in healthy human subjects.

It has been suggested that the therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) are mediated through changes in cortical inhibition (CI). However, in healthy human subjects the effects of rTMS on CI have been inconsistent. Therefore, this study sought to improve on the methodological limitations of previous studies by exploring several different rTMS-stimulus conditions on inhibition in the human motor cortex. In the first experiment, 12 healthy control subjects were randomly assigned to receive regular 1, 10 or 20 Hz rTMS in a counterbalanced order with sessions separated by at least 1 week. In the second experiment, 10 of these 12 subjects received priming rTMS (600 stimuli at 6 Hz followed by 600 stimuli at 1 Hz). Cortical inhibition was indexed using short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Corticospinal excitability was indexed using motor threshold and MEP amplitude. We found no significant overall change in SICI, although there was a significant correlation between changes in SICI with baseline SICI. Subjects with greater SICI at baseline tended to have reduction in SICI post-rTMS, whereas subjects with less SICI tended to have increase in SICI post-rTMS. There was also a significant lengthening of the CSP with higher stimulation frequencies compared to lower stimulation frequencies. These findings suggest that rTMS increases CI, particularly in subjects with reduced baseline inhibition, a finding consistent with the concept of homeostatic plasticity. Baseline physiological characteristics may be further explored as a method to select patients who may benefit from rTMS treatment.

Adult↗
PubMed2006

Dissociation of thalamic high frequency oscillations and slow component of sensory evoked potentials following damage to ascending pathways.

OBJECTIVE: Somatosensory evoked potentials (SEPs) recorded from the thalamus have a slow component and high frequency (approximately 1000 Hz) oscillations (HFOs). In this study, we examined how lesions in the sensory afferent pathway affect these components. METHODS: Thalamic SEPs to contralateral median nerve stimulation were recorded from deep brain stimulation electrodes in two patients. Patient 1 had spinal cord injury at the C4/5 level. Patient 2 had multiple sclerosis with mid brain lesions. Seven patients with no brain or cervical spinal cord lesions served as controls. RESULTS: In both patients, the low frequency component of the SEP (LF SEP) was delayed and/or prolonged and greatly decreased in amplitude compared with controls. HFOs were recorded in both patients. The latencies of onset and peak of the HFOs were approximately the same as those of the LF SEPs and their amplitudes were similarly reduced. However, their frequency was similar to that of the control group. Cortical SEPs were absent in both patients. CONCLUSIONS: Normal frequencies of thalamic HFOs in association with increased peak latencies, and decreased amplitudes provide further evidence that the HFOs are likely due to intrinsic oscillations in the thalamus rather than high frequency synchronous inputs. SIGNIFICANCE: Thalamic HFOs are closely associated with the LF SEP but are generated by a different mechanism.

Adult↗
PubMed2006

Motor cortex plasticity in Parkinson's disease and levodopa-induced dyskinesias.

Experimental models of Parkinson's disease have demonstrated abnormal synaptic plasticity in the corticostriatal system, possibly related to the development of levodopa-induced dyskinesias (LID). We tested the hypothesis that LID in Parkinson's disease is associated with aberrant plasticity in the human motor cortex (M1). We employed the paired associative stimulation (PAS) protocol, an experimental intervention involving transcranial magnetic stimulation (TMS) and median nerve stimulation capable of producing long-term potentiation (LTP) like changes in the sensorimotor system in humans. We studied the more affected side of 16 moderately affected patients with Parkinson's disease (9 dyskinetic, 7 non-dyskinetic) and the dominant side of 9 age-matched healthy controls. Motor-evoked potential (MEP) amplitudes and cortical silent period (CSP) duration were measured at baseline before PAS and for up to 60 min (T0, T30 and T60) after PAS in abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. PAS significantly increased MEP size in controls (+74.8% of baseline at T30) but not in patients off medication (T30: +0.07% of baseline in the non-dyskinetic, +27% in the dyskinetic group). Levodopa restored the potentiation of MEP amplitudes by PAS in the non-dyskinetic group (T30: +64.9% of baseline MEP) but not in the dyskinetic group (T30: -9.2% of baseline). PAS prolonged CSP duration in controls. There was a trend towards prolongation of CSP in the non-dyskinetic group off medications but not in the dyskinetic group. Levodopa did not restore CSP prolongation by PAS in the dyskinetic group. Our findings suggest that LTP-like plasticity is deficient in Parkinson's disease off medications and is restored by levodopa in non-dyskinetic but not in dyskinetic patients. Abnormal synaptic plasticity in the motor cortex may play a role in the development of LID.

Aged↗
PubMed2006

Cortical and spinal abnormalities in psychogenic dystonia.

OBJECTIVE: The pathophysiology of psychogenic dystonia has not been examined, but a growing body of literature suggests that abnormal sensory input from repetitive movements can lead to plastic cortical changes. Reduced cortical and spinal inhibition is well documented in organic dystonia. We tested the hypothesis that aberrant sensory input associated with abnormal posture may cause similar abnormalities by testing patients with psychogenic dystonia. METHODS: We assessed cortical and spinal inhibitory circuits and cortical activity associated with voluntary movement in 10 patients with clinically definite psychogenic dystonia, 8 patients with organic dystonia, and 12 age-matched healthy control subjects. RESULTS: Three measures of cortical inhibition, resting short- and long-interval intracortical inhibition and cortical silent period, were reduced in both psychogenic dystonia and organic dystonia. Cutaneous silent period mediated by spinal circuitries was increased in psychogenic and organic dystonia. Forearm spinal reciprocal inhibition was reduced in psychogenic dystonia. INTERPRETATION: Psychogenic and organic dystonia share similar physiological abnormalities. Previous findings of abnormal cortical and spinal excitability in organic dystonia may, in part, be a consequence rather than a cause of dystonia. Alternatively, these findings may represent endophenotypic abnormalities that predispose to both types of dystonia.

Adult↗
PubMed2006

Rapidly progressive sporadic dentatorubral pallidoluysian atrophy with intracytoplasmic inclusions and no CAG repeat expansion.

A 48-year-old man developed progressive hemidystonia and postural impairment with falls, followed by choreoathetosis, hyporeflexia, ataxia, supranuclear vertical gaze palsy, and dementia, lasting only 3.5 years from symptom onset to death. Family history and genetic testing were unrevealing. Neuropathology showed findings identical to genetic dentatorubral pallidoluysian atrophy (DRPLA), except for the absence of intranuclear inclusions and the presence of intracytoplasmic inclusions in the pons, striatum, thalamus, and subthalamic nucleus. This case expands the clinical and neuropathological spectrum of DRPLA and supports the hypothesis that aggregates may not be intrinsically pathogenic.

Disease Progression↗
PubMed2006

Rigidity and spasms from autoimmune encephalomyelopathies: stiff-person syndrome.

Stiff-person syndrome (SPS) is a disorder characterized by progressive muscle rigidity with superimposed painful muscle spasms and gait impairment due to continuous motor activity. Evidence has accumulated in favor of SPS representing an autoimmune, predominantly encephalomyelopathic disorder resulting from B-cell-mediated clonal production of autoantibodies against presynaptic inhibitory epitopes on the enzyme glutamic acid decarboxylase (GAD) and the synaptic membrane protein amphiphysin. Recognition of the clinical spectrum of SPS is important, particularly the upper-limb, cervical, and cranial nerve involvement that occurs in paraneoplastic variants. The correlation between antibody levels and severity of disease offers evidence for a pathogenic role for the anti-GAD and anti-amphiphysin autoantibodies. The scarcity of neuropathological correlates stand in sharp contrast with the severity of the disability in affected individuals and suggests that functional impairment of inhibitory circuits without structural damage is sufficient to develop the full clinical spectrum of SPS. The rarity of this condition limits the feasibility of controlled clinical trials in the treatment of SPS, but the available evidence suggest that drugs that increase cortical and spinal inhibition such as benzodiazepines and drugs that provide immune modulation such as intravenous immunoglobulin, plasmapheresis, and prednisone are effective treatments.

Autoantibodies↗
PubMed2006

Encephalopathy after whole-cell pertussis or measles vaccination: lack of evidence for a causal association in a retrospective case-control study.

BACKGROUND: Whole-cell pertussis (wP) and measles vaccines are effective in preventing disease but have also been suspected of increasing the risk of encephalopathy or encephalitis. Although many countries now use acellular pertussis vaccines, wP vaccine is still widely used in the developing world. It is therefore important to evaluate whether wP vaccine increases the risk of neurologic disorders. METHODS: A retrospective case-control study was performed at 4 health maintenance organizations. Records from January 1, 1981, through December 31, 1995, were examined to identify children aged 0 to 6 years old hospitalized with encephalopathy or related conditions. The cause of the encephalopathy was categorized as known, unknown or suspected but unconfirmed. Up to 3 controls were matched to each case. Conditional logistic regression was used to analyze the relative risk of encephalopathy after vaccination with diphtheria-tetanus-pertussis (DTP) or measles-mumps-rubella (MMR) vaccines in the 90 days before disease onset as defined by chart review compared with an equivalent period among controls indexed by matching on case onset date. RESULTS: Four-hundred fifty-two cases were identified. Cases were no more likely than controls to have received either vaccine during the 90 days before disease onset. When encephalopathies of known etiology were excluded, the odds ratio for case children having received DTP within 7 days before onset of disease was 1.22 (95% confidence interval [CI] = 0.45-3.31, P = 0.693) compared with control children. For MMR in the 90 days before onset of encephalopathy, the odds ratio was 1.23 (95% confidence interval = 0.51-2.98, P = 0.647). CONCLUSIONS: In this study of more than 2 million children, DTP and MMR vaccines were not associated with an increased risk of encephalopathy after vaccination.

Brain Diseases↗
PubMed2005

Multimodal imaging of brain reorganization in motor areas of the contralesional hemisphere of well recovered patients after capsular stroke.

Clinical recovery after stroke can be significant and has been attributed to plastic reorganization and recruitment of novel areas previously not engaged in a given task. As equivocal results have been reported in studies using single imaging or electrophysiological methods, here we applied an integrative multimodal approach to a group of well-recovered chronic stroke patients (n = 11; aged 50-81 years) with left capsular lesions. Focal activation during recovered hand movements was assessed with EEG spectral analysis and H2(15)O-PET with EMG monitoring, cortico-cortical connectivity with EEG coherence analysis (cortico-cortical coherence) and corticospinal connectivity with transcranial magnetic stimulation (TMS). As seen from comparisons with age-matched controls, our patients showed enhanced recruitment of the lateral premotor cortex of the lesioned hemisphere [Brodmann area (BA) 6], lateral premotor and to a lesser extent primary sensorimotor and parietal cortex of the contralesional hemisphere (CON-H; BA 4 and superior parietal lobule) and left cerebellum (patients versus controls, Z > 3.09). EEG coherence analysis showed that after stroke cortico-cortical connections were reduced in the stroke hemisphere but relatively increased in the CON-H (ANOVA, contrast analysis, P < 0.05), suggesting a shift of functional connectivity towards the CON-H. Nevertheless, fast conducting corticospinal transmission originated exclusively from the lesioned hemisphere. No direct ipsilateral motor evoked potentials (MEPs) could be elicited with TMS over the contralesional primary motor cortex (iM1) in stroke patients. We conclude that (i) effective recovery is based on enhanced utilization of ipsi- and contralesional resources, (ii) basic corticospinal commands arise from the lesioned hemisphere without recruitment of ('latent') uncrossed corticospinal tract fibres and (iii) increased contralesional activity probably facilitates control of recovered motor function by operating at a higher-order processing level, similar to but not identical with the extended network concerned with complex movements in healthy subjects.

Aged↗
PubMed2005

Representation of facial muscles in human motor cortex.

Whether there is a projection from the primary motor cortex (M1) to upper facial muscles and how the facial M1 area is modulated by intracortical inhibitory and facilitatory circuits remains controversial. To assess these issues, we applied transcranial magnetic stimulation (TMS) to the M1 and recorded from resting and active contralateral (C-OOc) and ipsilateral orbicularis oculi (I-OOc), and contralateral (C-Tr) and ipsilateral triangularis (I-Tr) muscles in 12 volunteers. In five subjects, the effects of stimulating at different scalp positions were assessed. Paired TMS at interstimulus intervals (ISIs) of 2 ms were used to elicit short interval intracortical inhibition (SICI) and ISI of 10 ms for intracortical facilitation (ICF). Long interval intracortical inhibition (LICI) was evaluated at ISIs between 50 and 200 ms, both at rest and during muscle activation. The silent period (SP) was also determined. C-OOc and I-OOc responses were recorded in all subjects. The optimal position for eliciting C-OOc responses was lateral to the hand representation in all subjects and MEP amplitude markedly diminished when the coil was placed 2 cm away from the optimal position. For the I-OOc, responses were present in more scalp sites and the latency decreased with more anterior placement of the coil. C-Tr response was recorded in 10 out of 12 subjects and the I-Tr muscle showed either no response or low amplitude response, probably due to volume conduction. SICI and ICF were present in the C-OOc and C-Tr, but not in the I-OOc muscle. Muscle activation attenuated SICI and ICF. LICI at rest showed facilitation at 50 ms ISI in all muscles, but there was no significant inhibition at other ISIs. There was no significant inhibition or facilitation with the LICI protocol during muscle contraction. The SP was present in the C-OOc, C-Tr and I-OOc muscles and the mean durations ranged from 92 to 104 ms. These findings suggest that the I-OOc muscle response is probably related to the first component (R1) of the blink reflex. There is M1 projection to the contralateral upper and lower facial muscles in humans and the facial M1 area is susceptible to cortical inhibition and facilitation, similar to limb muscles.

Acoustic Stimulation↗
PubMed2005

Effect of low-frequency repetitive transcranial magnetic stimulation on interhemispheric inhibition.

We studied the effects of 1-Hz repetitive transcranial magnetic stimulation (rTMS) on the excitability of interhemispheric connections in 13 right-handed healthy volunteers. TMS was performed using figure-eight coils, and surface electromyography (EMG) was recorded from both first dorsal interosseous (FDI) muscles. A paired-pulse method with a conditioning stimulus (CS) to the motor cortex (M1) followed by a test stimulus to the opposite M1 was used to study the interhemispheric inhibition (ppIHI). Both CS and TS were adjusted to produce motor-evoked potentials of approximately 1 mV in the contralateral FDI muscles. After baseline measurement of right-to-left IHI (pre-RIHI) and left-to-right IHI (pre-LIHI), rTMS was applied over left M1 at 1 Hz with 900 stimuli at 115% of resting motor threshold. After rTMS, ppIHI was studied using both the pre-rTMS CS (post-RIHI and post-LIHI) and an adjusted post-rTMS CS set to produce 1-mV motor evoked potentials (MEPs; post-RIHI(adj) and post-LIHI(adj)). The TS was set to produce 1-mV MEPs. There was a significant reduction in post-LIHI (P = 0.0049) and post-LIHI(adj) (P = 0.0169) compared with pre-LIHI at both interstimulus intervals of 10 and 40 ms. Post-RIHI was significantly reduced compared with pre-RIHI (P = 0.0015) but pre-RIHI and post-RIHI(adj) were not significantly different. We conclude that 1-Hz rTMS reduces IHI in both directions but is predominantly from the stimulated to the unstimulated hemisphere. Low-frequency rTMS may be used to modulate the excitability of IHI circuits. Treatment protocols using low-frequency rTMS to reduce cortical excitability in neurological and psychiatric conditions need to take into account their effects on IHI.

Adult↗
PubMed2005

Interactions between long latency afferent inhibition and interhemispheric inhibitions in the human motor cortex.

Various inhibitory pathways exist in the human brain which are crucial in modulating motor cortex output and they can be investigated non-invasively using transcranial magnetic stimulation. Interhemispheric inhibition (IHI) is one form of cortical inhibition. It can be elicited by stimulation of the opposite motor cortex at interstimulus intervals (ISIs) of 10 ms (IHI10) or 40 ms (IHI40) and inhibitions at these intervals are probably mediated by different mechanisms. Peripheral sensory stimulation can also inhibit the motor cortex. Median nerve stimulation produces long latency afferent inhibition (LAI) at ISI 200 ms. LAI inhibits another form of cortical inhibition known as long interval intracortical inhibition (LICI) and a study that examined the interaction between IHI10 and LICI hypothesized that they are mediated by an overlapping population of inhibitory neurones. We tested this hypothesis by examining the interaction between IHI10, IHI40 and LAI. With increasing test MEP amplitude LAI, IHI10 and IHI40 all decreased. There was no correlation between the strength of LAI, IHI10 and IHI40. In the presence of LAI, IHI10 was slightly but significantly reduced compared to IHI10 alone. There was no correlation between the reduction in IHI10 in the presence of LAI and the strength of LAI or IHI10. In the presence of LAI, IHI40 was significantly reduced compared to IHI40 alone. LAI produced a greater decrease in IHI40 than in IHI10. The decrease in IHI40 in the presence of LAI strongly correlated with the strength of LAI but not with the strength of IHI40. Reducing the strength of LAI, IHI10 and IHI40 still resulted in similar interaction between IHI10 and LAI but markedly decreased the effect of LAI on IHI40. We conclude that LAI and IHI10 do not directly inhibit each other but LAI probably inhibits IHI40. LICI is more likely to be related to IHI40 than to IHI10.

Adult↗
PubMed2005

Task-dependent intracortical inhibition is impaired in focal hand dystonia.

We tested whether task-dependent modulation of inhibition within the motor cortex is impaired in patients with dystonia. Paired-pulse transcranial magnetic stimulation (TMS) at an interstimulus interval of 2 msec was used to measure the effect of two different tasks on short ISI intracortical inhibition (SICI) in dystonic and normal subjects. In two experiments, SICI of the fourth dorsal interosseus (4DIO) and abductor pollicis brevis (APB) muscles were measured before and at the end of the training task. In the first experiment, subjects performed a nonselective task consisting of abducting the thumb, where the APB acted as agonist and the 4DIO as synergist. In the second experiment, the function of the 4DIO was changed as the subjects were asked to consciously inhibit this muscle while abducting the thumb (selective task). Therefore, while the APB was activated in both tasks, the 4DIO was activated in the nonselective task but was in the inhibitory surround in the selective task. We found that performance of the selective but not the nonselective task resulted in increased SICI in the 4DIO of normal but not in dystonic subjects. We conclude that task-dependent SICI is disturbed in patients with dystonia.

Dystonic Disorders↗
PubMed2005

Tracking vaccine lot lifecycles using reports to the vaccine adverse event reporting system (VAERS).

PURPOSE: There is currently no systematically available information available on how rapidly a specific lot of vaccine is used once distributed. We used data from reports to the Vaccine Adverse Event Reporting System (VAERS) to develop a proxy means of surveillance for the lifecycle of selected vaccine lots. METHODS: A convenience sample, consisting of selected lots of: diphtheria, tetanus, and acellular pertussis (DTaP), Haemophilus influenzae type b (Hib), Hepatitis B, and varicella vaccines, was selected for lifecycle analysis. Assuming that circulation of a vaccine lot is proportional to vaccine-specific adverse event (AE) reporting for that vaccine type, we constructed Gamma distributed usage models and compared them with lot-specific VAERS reports to estimate the actual lifecycle of lots in the system. RESULTS: Evidence of lot circulation was detected within 1-2 months, and a peak was observed 3-4 months after the vaccine release date for most of the study vaccines. Ninety percent of the vaccine doses in each lot were estimated to be used within 5-9 months of distribution. The length of time a vaccine lot was in use ranged from 5 to 17 months from earliest vaccination date. CONCLUSIONS: Our modeled and inferred administration of the selected lots of different vaccines were concordant. This method may be useful for spatial and temporal tracking of vaccine lot utilization.

Models, Theoretical↗
PubMed2005

Cortical plasticity following upper extremity injury and reconstruction.

Today's view of the adult central nervous system is that of an adaptive and responsive system. Plastic surgeons, because of the motor and sensory reconstructions they perform, need to have an understanding of brain plasticity following upper extremity injury, reconstruction, and rehabilitation. Functional MRI and transcranial magnetic stimulation can identify cortical plasticity in humans. For instance, these techniques have identified changes in excitability and body site representation in the motor cortex in patients following motor reconstruction and motor relearning. Therefore, cortical plasticity and its manipulation may be an important contributor to functional outcome following reconstruction. In the future, cortical plasticity may have implications for reconstruction and rehabilitation.

Amputation, Traumatic↗
PubMed2005

Reduced cerebellar inhibition in schizophrenia: a preliminary study.

OBJECTIVE: Postmortem and structural imaging studies suggest that patients with schizophrenia have disrupted cerebellar activity. It has been speculated that these abnormalities mediate disorganized thought processes and psychosis. The authors' goal was to use transcranial magnetic stimulation to measure cerebellar inhibition, a proxy of cerebellar activity, as the principal output of the cerebellum is inhibitory. METHOD: Cerebellar inhibition was accomplished by delivering a magnetic cerebellar conditioning stimulus 5-15 msec before a magnetic test stimulus to the motor cortex. The cerebellar conditioning stimulus inhibits the size of the motor evoked potential produced by the test stimulus by approximately 50%. Ten patients with schizophrenia and 10 healthy comparison subjects completed the cerebellar inhibition protocol. RESULTS: Patients with schizophrenia demonstrated significant deficits in cerebellar inhibition compared with healthy subjects. CONCLUSIONS: The authors conclude that deficits in cerebellar inhibitory activity in schizophrenia may be the result of an abnormality in the cerebellum or disrupted cerebellar-thalamic-cortical connectivity.

Adult↗