Recent imaging studies in healthy controls with a conditional stop signal reaction time (RT) task have implicated the subthalamic nucleus (STN) in response inhibition and the pre-supplementary motor area (pre-SMA) in conflict resolution. Parkinson's disease (PD) is characterized by striatal dopamine deficiency and overactivity of the STN and underactivation of the pre-SMA during movement. We used the conditional stop signal RT task to investigate whether PD produced similar or dissociable effects on response initiation, response inhibition and response initiation under conflict. In addition, we also examined inhibition of prepotent responses on three cognitive tasks: the Stroop, random number generation and Hayling sentence completion. PD patients were impaired on the conditional stop signal reaction time task, with response initiation both in situations with or without conflict and response inhibition all being significantly delayed, and had significantly greater difficulty in suppressing prepotent or habitual responses on the Stroop, Hayling and random number generation tasks relative to controls. These results demonstrate the existence of a generalized inhibitory deficit in PD, which suggest that PD is a disorder of inhibition as well as activation and that in situations of conflict, executive control over responses is compromised.

The subthalamic nucleus (STN) is hypothesized to play a central role in the rapid stopping of movement in reaction to a stop signal. Single-unit recording evidence for such a role is sparse, however, and it remains uncertain how that role relates to the disparate functions described for anatomic subdivisions of the STN. Here we address that gap in knowledge using non-human primates and a task that distinguishes reactive and proactive action inhibition, switching and skeletomotor functions. We found that specific subsets of STN neurons have activity consistent with causal roles in reactive action stopping or switching. Importantly, these neurons were strictly segregated to a ventromedial region of STN. Neurons in other subdivisions encoded task dimensions such as movement per se and proactive control. We propose that the involvement of STN in reactive control is restricted to its ventromedial portion, further implicating this STN subdivision in impulse control disorders.

Changes of cognitive function in PD have been extensively documented and defined as a ‘frontal’ type executive dysfunction. One of the main components of this executive dysfunction is the impairment of verbal fluency. The aim of the present study was to assess semantic and phonemic fluency in a large sample of PD patients and to investigate the effect of clinical and sociodemographic variables on verbal fluency in this patient group.Three hundred patients with idiopathic Parkinson's disease who were consecutive referrals to our clinic and 50 age and education matched healthy controls completed the phonemic and semantic verbal fluency tasks. Both phonemic and semantic verbal fluency were significantly impaired in PD patients relative to matched controls. Stage of illness, presence of depression, education and age influenced verbal fluency measures. Regression analyses established that global measures of cognitive ability (MMSE) and executive function (FAB) and side of onset of motor symptoms predicted 36–37% of variance of phonemic or semantic verbal fluency measures. Thus, future studies aimed at assessing cognitive functioning in PD patients treated by deep brain stimulation (DBS) should adequately take into account several factors (stage of illness, depression, executive functioning) which may potentially influence performance on verbal fluency tasks.

We describe the clinical impact of the RehaCom computerized cognitive training program instituted in the International Neurological Restoration Center for rehabilitation of brain injury patients. Fifty patients admitted from 2008 through 2010 were trained over 60 sessions. Attention and memory functions were assessed with a pre-and post-treatment design, using the Mini-Mental State Examination, Wechsler Memory Scale and Trail Making Test (Parts A and B). Negative effects were assessed, including mental fatigue, headache and eye irritation. The program's clinical usefulness was confi rmed, with 100% of patients showing improved performance in trained functions. KEYWORDS Lessons from the FieldThe prevalence of TBI in the study group was 58% (29/50), followed by 42% (21/50) for stroke. Most, 68% (34/50), were men; and 66% (33/50) had completed between 10 and 15 years of formal education. Sixty-eight percent (34/50) were aged 20 to 39 years. Over half the subjects in rehabilitation had been affected for one to fi ve years.Despite impaired attention and memory processes, overall cognitive impairment was mild with a Mini-Mental State Examination (MMSE) of 20-24 points in 66% (33/50) and moderate (MMSE: 15-19 points) in 34% (17/50).All patients had motor disorders, including hemiparesis, hemiplegia and cerebellar ataxia; 76% (38/50) had vision problems (hemianopsia, diplopia, artifi cial eye); and 14% (7/50) had diminished hearing.Clinical usefulness of the software was assessed using the following variables:• Flexibility: Proportion of patients included in the study who participated in therapy irrespective of sensorimotor defi cits.• Dynamics: Personalized increase in task diffi culty level according to individual patient progress. Procedures and Ethics Therapists familiarized themselves with the program for two months before commencement of patient training. A neuro psychologist performed an intial evaluation during the standard assessment week required for all patients on admission to CIREN. An external evaluator, a psychologist, administered attention and memory tests before and after training, each patient serving as his or her own control.The study protocol was approved by CIREN's ethics committee.Patients provided written informed consent before enrolling in training.Patients received 60 training sessions over 12 weeks, divided into fi ve 50-minute sessions per week. All sessions were held in the morning in a laboratory designed for this purpose, where up to four patients worked simultaneously under supervision by two specialists. Patients were monitored for possible negative effects during training.Data processing Descriptive statistics were used (percentage, mean and standard deviation). To assess training effect, differences between pre-and post-training measures of attention and memory test performance were analyzed using the Student t test with statistical signifi cance set at p <0.05. RESULTSFlexibility One hundred percent of the patients were able to enroll in treatment, irrespective of sensory a...

Abstract. OBJECTIVE:To generate normative data on the Hopkins Verbal Learning Test-Revised (HVLT-R) across 11 countries in Latin America, with country-specific adjustments for gender, age, and education, where appropriate. METHOD: The sample consisted of 3,977 healthy adults who were recruited from Argentina, Bolivia, Chile, Cuba, El Salvador, Guatemala, Honduras, Mexico, Paraguay, Peru, and, Puerto Rico. Each subject was administered the HVLT-R as part of a larger neuropsychological battery. A standardized five-step statistical procedure was used to generate the norms. RESULTS: The final multiple linear regression models explained 17-45% of the variance in HVLT-R scores. Although t-tests showed significant differences between men and women in Guatemala on the HVLT-R, it was a small effect size. As a result, gender-adjusted norms were not generated.