Large and fast human pyramidal neurons associate with intelligence.

It is generally assumed that human intelligence relies on efficient processing by neurons in our brain. Although grey matter thickness and activity of temporal and frontal cortical areas correlate with IQ scores, no direct evidence exists that links structural and physiological properties of neurons to human intelligence. Here, we find that high IQ scores and large temporal cortical thickness associate with larger, more complex dendrites of human pyramidal neurons. We show in silico that larger dendritic trees enable pyramidal neurons to track activity of synaptic inputs with higher temporal precision, due to fast action potential kinetics. Indeed, we find that human pyramidal neurons of individuals with higher IQ scores sustain fast action potential kinetics during repeated firing. These findings provide the first evidence that human intelligence is associated with neuronal complexity, action potential kinetics and efficient information transfer from inputs to output within cortical neurons.

Predictors of cognitive and psychosocial outcome after STN DBS in Parkinson's Disease.

OBJECTIVE: To find predictors of cognitive decline and quality of life 1 year after bilateral subthalamic nucleus deep brain stimulation (STN DBS) in Parkinson's disease (PD). METHODS: A total of 105 patients were evaluated with a comprehensive neuropsychological assessment before and 12 months after surgery. A control group of 40 PD patients was included to control for effects of repeated testing and disease progression. The authors determined individual changes in cognition, mood and quality of life using a statistical method that controls for multiple comparisons, and performed logistic regression analyses to assess predictors of cognitive changes and quality of life. RESULTS: 12 months after surgery, the improvement in motor function was 41% (Unified Parkinson's Disease Rating Scale Part 3 score in off). The STN group showed a large improvement in quality of life compared with the control group (Cohen d=0.9). At the individual level, 32% (95% CI 22 to 40) of the STN group showed a substantial improvement in quality of life. 36% (95% CI 27 to 46) of the STN patients showed a profile of cognitive decline compared with the control group. Mood improved in 16 STN patients and declined in 16 subjects. Impaired attention, advanced age and a low l-dopa response at baseline predicted cognitive decline, whereas a high l-dopa response at baseline predicted an improvement in quality of life. Postoperative decrease in dopaminergic medication was not related to cognitive decline. CONCLUSIONS: STN DBS improves quality of life. However, a profile of cognitive decline can be found in a significant number of patients. l-dopa response, age and attention at baseline are predictors of cognitive and psychosocial outcome.

Impaired emotion recognition in music in Parkinson's disease.

Music has the potential to evoke strong emotions and plays a significant role in the lives of many people. Music might therefore be an ideal medium to assess emotion recognition. We investigated emotion recognition in music in 20 patients with idiopathic Parkinson's disease (PD) and 20 matched healthy volunteers. The role of cognitive dysfunction and other disease characteristics in emotion recognition was also evaluated. We used 32 musical excerpts that expressed happiness, sadness, fear or anger. PD patients were impaired in recognizing fear and anger in music. Fear recognition was associated with executive functions in PD patients and in healthy controls, but the emotion recognition impairments of PD patients persisted after adjusting for executive functioning. We found no differences in the recognition of happy or sad music. Emotion recognition was not related to depressive symptoms, disease duration or severity of motor symptoms. We conclude that PD patients are impaired in recognizing complex emotions in music. Although this impairment is related to executive dysfunction, our findings most likely reflect an additional primary deficit in emotional processing.

Multivariate normative comparisons.

In neuropsychological evaluations and single case research generally a number of tests are administered, since the interest is not in a single, but in multiple characteristics of a patient. The typical problem is to decide whether or not a patient is different from normal controls with respect to one or more of these characteristics. Consideration of each characteristic separately entails an increased risk of a false positive decision (a wrongful decision that the patient is abnormal, or a type 1 error). From a statistical point of view this calls for a multivariate analysis. In this paper, we propose two approaches to perform normative comparisons for such multivariate data: Bonferroni corrected univariate comparisons and a multivariate comparison. Both approaches allow for the testing of unidirectional (two-sided) as well as directional (one-sided) hypothesis, i.e. the hypothesis that a patient deviates in a negative sense from the norm. Monte Carlo simulations were performed to check if the type I error of both approaches is adequately controlled, and to investigate the power of both approaches to detect deviation from the norm. The results indicate that the type I error rate of both approaches is correct, even in small samples. The results also indicate that the power is higher for the univariate approach if the normative sample size is very small (i.e. just exceeds the number of tests administered). In larger samples, the multivariate comparison has in general increased power. We illustrate both approaches with a clinical example of patients with Parkinson disease, who received deep brain stimulation to alleviate motor symptoms, and who were neuropsychologically evaluated to detect possible cognitive side effects.

Unilateral pallidotomy versus bilateral subthalamic nucleus stimulation in PD--a comparison of neuropsychological effects.

OBJECTIVE: To compare the cognitive and behavioural effects of unilateral pallidotomy and bilateral subthalamic nucleus (STN) stimulation. METHODS: After baseline examination 34 patients were randomly assigned to unilateral pallidotomy (4 left-sided, 10 right-sided) or bilateral STN stimulation (n = 20). At baseline and six and twelve months after surgery we administered neuropsychological tests of language, memory, visuospatial function, mental speed and executive functions. Also a depression rating scale, and self and proxy ratings of memory and dysexecutive symptoms were administered. RESULTS: Six months after surgery, the STN group and the pallidotomy group differed significantly in change from baseline in number of errors on two tests of executive functioning. After 12 months the STN group reported less positive affect compared with baseline than the pallidotomy group. One patient in the STN group showed an overall cognitive deterioration due to complications. CONCLUSIONS: Although we need larger groups to draw firm conclusions, our results suggest that bilateral STN stimulation has slightly more negative effects on executive functioning than unilateral pallidotomy.

Hyperbaric oxygen therapy for cognitive disorders after irradiation of the brain.

PURPOSE: Analysis of the feasibility and effect of hyperbaric oxygen treatment (HBO) on cognitive functioning in patients with cognitive disorders after irradiation of the brain. PATIENTS AND METHOD: Seven patients with cognitive impairment after brain irradiation, with an interval of at least 1.5 years after treatment, were treated with 30 sessions of HBO in a phase I-II study. A comprehensive neuropsychological test battery was performed before treatment, at 3 and 6 months thereafter. Patients were randomized into an immediate treatment group and a delayed treatment group. The delayed group had a second neuropsychological test at 3 months without treatment in that period and started HBO thereafter. RESULTS: All eligible patients completed the HBO treatment and the extensive neuropsychological testing. One out of seven patients had a meaningful improvement in neuropsychological functioning. At 3 months there was a small, but not significant benefit in neuropsychological performance for the group with HBO compared to the group without HBO treatment. Six out of seven patients eventually showed improvement after HBO in one to nine (median 2.5) of the 31 tests, although without statistical significance. CONCLUSION: HBO treatment was feasible and resulted in a meaningful improvement of cognitive functioning in one out of seven patients. Overall there was a small but not significant improvement.