Interictal epileptiform activity and autism.

Many individuals with autism have epileptiform discharges on their EEG without having definite clinical seizures. The clinical significance of epileptiform activity in patients with autism is controversial. Some consider it an epiphenomenon of the underlying condition that should be ignored, and others believe that frequent spikes may contribute to the cognitive impairment and advocate treatment. Several studies have reported variable rates of epileptiform activity and variable response to treatment. There is an urgent need to conduct controlled clinical trials to assess the true incidence of epileptiform activity in children with autism, develop a risk assessment model, and study the effectiveness of treatment. This article is part of a Special Issue entitled "Autism and Epilepsy".

Theta oscillations mediate interaction between prefrontal cortex and medial temporal lobe in human memory.

The medial temporal lobe (MTL) and the prefrontal cortex (PFC) are known to be critical structures for human memory processes. Furthermore, it has been suggested that they are part of a memory network. Although memory-modulated interaction between PFC and MTL has been observed at the hemodynamic level, it remains unclear what the neuronal process is that mediates the communication between these 2 areas. Experiments in rodents suggest that field oscillations in the theta band (4-8 Hz) facilitate PFC-MTL interaction. No such evidence has been reported in humans. To address this problem, cortical electrical activity from MTL, PFC, and lateral temporal lobe was recorded from implanted electrode grids in 3 epilepsy patients performing a verbal free recall task. The data were analyzed using a parametric spectral method to obtain estimates of power, coherence, and Granger causality. A task-modulated increase in coherence values between PFC and MTL was seen during free recall as opposed to a baseline condition. Concurrently, the number of coherent PFC-MTL site pairs was significantly increased during recall. Granger causality analysis further revealed that the increased coherence is a consequence of higher bidirectional information flow between the 2 regions, with a generally greater driving from MTL to PFC, namely, (MTL-->PFC) > (PFC-->MTL).

Seizure recurrence following epilepsy surgery: is post-operative EEG helpful?

OBJECTIVES: We examined whether the relationship between interictal epileptiform discharges (IED) on post-operative EEG and seizure recurrence after epilepsy surgery was different in patients with neocortical and mesiotemporal resections. METHODS: We reviewed the records of 93 consecutive patients who underwent epilepsy surgery at our center and who had adequate post-operative follow-up and a post-operative EEG to determine the type of surgery, the recurrence of seizures and the presence of IED on post-operative EEG. RESULTS: Chi-square test revealed that for the entire group, there was a significant relationship between the presence of IED and seizure recurrence. However, this relationship was significant in neocortical surgery but not in mesiotemporal surgery. Time distribution of seizure recurrence revealed that in more than half the cases, seizures recurred with the first 3 months. Time distribution was not influenced by the presence of IED. CONCLUSIONS: This study revealed that IED on early post-operative EEG correlate with seizure recurrence in neocortical but not mesiotemporal surgeries and may be used to guide patient counseling in this group of patients.

Effects of donepezil on verbal memory after semantic processing in healthy older adults.

OBJECTIVE: To learn if acetylcholinesterase inhibitors alter verbal recall by improving semantic encoding in a double-blind randomized placebo-controlled trial. BACKGROUND: Cholinergic supplementation has been shown to improve delayed recall in adults with Alzheimer disease. With functional magnetic resonance imaging, elderly adults, when compared with younger participants, have reduced cortical activation with semantic processing. There have been no studies investigating the effects of cholinergic supplementation on semantic encoding in healthy elderly adults. METHOD: Twenty elderly participants (mean age 71.5, SD+/-5.2) were recruited. All underwent memory testing before and after receiving donepezil (5 mg, n=11 or 10 mg, n=1) or placebo (n=8) for 6 weeks. Memory was tested using a Levels of Processing task, where a series of words are presented serially. Subjects were either asked to count consonants in a word (superficially process) or decide if the word was "pleasant" or "unpleasant" (semantically process). RESULTS: After 6 weeks of donepezil or placebo treatment, immediate and delayed recall of superficially and semantically processed words was compared with baseline performance. Immediate and delayed recall of superficially processed words did not show significant changes in either treatment group. With semantic processing, both immediate and delayed recall performance improved in the donepezil group. CONCLUSIONS: Our results suggest that when using semantic encoding, older normal subjects may be aided by anticholinesterase treatment. However, this treatment does not improve recall of superficially encoded words.

Ipsilateral motor activation during unimanual and bimanual motor tasks.

OBJECTIVE: To test for the presence and possible asymmetry of ipsilateral motor activation during unimanual and bimanual motor tasks. METHODS: Twelve right-handed healthy subjects underwent motor evoked potential (MEP) measurement of one hand (target-hand) while the other hand (task-hand) performed different motor tasks. The target-hand was either at rest (first experiment) or performed a Perdue PegBoard task (second experiment). The task-hand was either at rest, performed a simultaneous pegboard task, or rotated a coin (second experiment). RESULTS: In the first experiment, the motor task resulted in significant increase in MEP area in the target-hand, regardless which hand was the task-hand, with a greater increase when the left hand was the task-hand. In the second experiment, ipsilateral motor activation was not present for either hand, however, when the right hand was the task-hand, performance of continuous coin rotation by the right hand resulted in a significant decrease in the MEP area of the left hand. CONCLUSIONS: Hemispheric asymmetry and task-dependence of ipsilateral motor cortex activation supports the postulate that motor activity may start bilaterally with subsequent interhemispheric inhibition. Furthermore, in right-handers, the left motor cortex is either more active in ipsilateral hand movements or exerts more effective inhibitory control over the right motor cortex than vice versa. SIGNIFICANCE: We suggest that hemispheric asymmetry in ipsilateral motor control is a factor in determining motor dominance in right-handed individuals.

Creative innovation with temporal lobe epilepsy and lobectomy.

OBJECTIVES: Some patients with left temporal degeneration develop visual artistic abilities. These new artistic abilities may be due to disinhibition of the visuo-spatially dominant right hemisphere. Many famous artists have had epilepsy and it is possible that some may have had left temporal seizures (LTS) and this left temporal dysfunction disinhibited their right hemisphere. Alternatively, unilateral epilepsy may alter intrahemispheric connectivity and right anterior temporal lobe seizures (RTS) may have increased these artists' right hemisphere mediated visual artistic creativity. METHODS: To test the disinhibition versus enhanced connectivity hypotheses we studied 9 participants with RTS and 9 with left anterior temporal seizures (LTS) who underwent unilateral lobectomy for the treatment of medically refractory epilepsy. Creativity was tested using the Torrance Test of Creative Thinking (TTCT). RESULTS AND CONCLUSIONS: There were no between group differences in either the verbal or figural scores of the TTCT, suggesting that unilateral anterior temporal ablation did not enhance visual artistic ability; however, for the RTS participants' figural creativity scores were significantly higher than verbal scores. Whereas these results fail to support the left temporal lobe disinhibition postulate of enhanced figural creativity, the finding that the patients with RTS had better figural than verbal creativity suggests that their recurrent right hemispheric seizures lead to changes in their right hemispheric networks that facilitated visual creativity. To obtain converging evidence, studies on RTS participants who have not undergone lobectomy will need to be performed.

Quantitative complexity analysis in multi-channel intracranial EEG recordings form epilepsy brains.

Epilepsy is a brain disorder characterized clinically by temporary but recurrent disturbances of brain function that may or may not be associated with destruction or loss of consciousness and abnormal behavior. Human brain is composed of more than 10 to the power 10 neurons, each of which receives electrical impulses known as action potentials from others neurons via synapses and sends electrical impulses via a sing output line to a similar (the axon) number of neurons. When neuronal networks are active, they produced a change in voltage potential, which can be captured by an electroencephalogram (EEG). The EEG recordings represent the time series that match up to neurological activity as a function of time. By analyzing the EEG recordings, we sought to evaluate the degree of underlining dynamical complexity prior to progression of seizure onset. Through the utilization of the dynamical measurements, it is possible to classify the state of the brain according to the underlying dynamical properties of EEG recordings. The results from two patients with temporal lobe epilepsy (TLE), the degree of complexity start converging to lower value prior to the epileptic seizures was observed from epileptic regions as well as non-epileptic regions. The dynamical measurements appear to reflect the changes of EEG's dynamical structure. We suggest that the nonlinear dynamical analysis can provide a useful information for detecting relative changes in brain dynamics, which cannot be detected by conventional linear analysis.

Effect of vagus nerve stimulation on creativity and cognitive flexibility.

OBJECTIVE: The purpose of this study was to determine whether vagus nerve stimulation influences cognitive flexibility and creativity. METHODS: Ten subjects, in whom vagus nerve stimulators had been implanted for the treatment of intractable seizures, performed tasks that assessed cognitive flexibility (solving anagrams), creativity (Torrance Test), and memory (Hopkins Verbal Learning Test) during actual and sham vagus nerve stimulation. RESULTS: Vagus nerve stimulation impaired cognitive flexibility and creativity, but these results could not be explained by the induction of a general encephalopathy because VNS did not impair learning and improved retention. CONCLUSIONS: The means by which vagus nerve stimulation impairs cognitive flexibility and creative thinking is probably related to increased activity of the locus coeruleus-central adrenergic system that increases the signal-to-noise ratio and improves the brain's ability to attend to sensory input, but decreases its ability to recruit large-scale networks.

The influence of vagus nerve stimulation on memory.

BACKGROUND: Vagus nerve stimulation (VNS) has been shown to improve memory. OBJECTIVE: The purpose of this study was to learn at which stage of memory formation this influence occurs. METHODS: Ten subjects who had been implanted with vagus nerve stimulators for the treatment of intractable seizures performed tasks that assessed learning and retention (Hopkins Verbal Learning Test) during actual and sham VNS. RESULTS: We found that VNS had no effect on learning but enhanced consolidation, which led to improved retention. CONCLUSIONS: The means by which VNS improves retention is probably related to the increased activity in the nucleus of the tractus solitarius and the locus coeruleus-central adrenergic system that activates the amygdala and increases long-term potentiation in the hippocampus.

Lateralized asymmetry of facial motor evoked potentials.

BACKGROUND: There is considerable evidence that emotions are expressed more intensely on the left side of the face. This asymmetry could reflect a right hemisphere advantage in processing emotional material or an asymmetry in corticobulbar motor systems. Transcranial magnetic stimulation (TMS) was used to test for lateralized asymmetry in the cortical control of muscles of facial expression in the lower face. METHODS: We administered TMS to the motor cortex of 50 subjects during contraction of bilateral orbicularis oris muscles. We analyzed motor evoked potentials (MEPs) with a repeated measures analysis of variance (ANOVA) using hemisphere stimulated and orbicularis oris side recorded as within subject factors. RESULTS: TMS elicited contralateral MEPs in 42 of 50 subjects. Forty of these 42 subjects showed bilateral MEPs. The ANOVA showed a significant main effect of face side, such that MEPs elicited in left face were larger than in right face (p < 0.0001). The analysis also showed a significant interaction between the hemisphere stimulated and face side, such that the difference between contralateral and ipsilateral MEPs with right brain TMS was greater than with left brain TMS (p < 0.0001). CONCLUSIONS: The results provide evidence of lateralized asymmetry of corticobulbar projections to muscles of facial expression in the lower face.

Progressive affective aprosodia and prosoplegia.

The right frontal lobe is important for the expression of emotional prosody, emotional faces, and automatic speech. The authors describe a woman who presented with progressive expressive affective aprosodia, affective prosoplegia, amusia, and loss of automatic speech but with an intact ability to understand emotional prosody and faces as well as express and understand syntactic prosody. MRI showed predominant right frontal cortical atrophy. The authors suggest that this patient has a form of frontotemporal dementia, analogous to primary progressive aphasia but disrupting right frontal lobe-mediated functions.