Neural correlates of unstructured motor behaviors.

OBJECTIVE: We studied the relationship between uninstructed, unstructured movements and neural activity in three epilepsy patients with intracranial electroencephalographic (iEEG) recordings. APPROACH: We used a custom system to continuously record high definition video precisely time-aligned to clinical iEEG data. From these video recordings, movement periods were annotated via semi-automatic tracking based on dense optical flow. MAIN RESULTS: We found that neural signal features (8-32 Hz and 76-100 Hz power) previously identified from task-based experiments are also modulated before and during a variety of movement behaviors. These movement behaviors are coarsely labeled by time period and movement side (e.g. 'Idle' and 'Move', 'Right' and 'Left'); movements within a label can include a wide variety of uninstructed behaviors. A rigorous nested cross-validation framework was used to classify both movement onset and lateralization with statistical significance for all subjects. SIGNIFICANCE: We demonstrate an evaluation framework to study neural activity related to natural movements not evoked by a task, annotated over hours of video. This work further establishes the feasibility to study neural correlates of unstructured behavior through continuous recording in the epilepsy monitoring unit. The insights gained from such studies may advance our understanding of how the brain naturally controls movement, which may inform the development of more robust and generalizable brain-computer interfaces.

Abnormalities of cortical thickness in postictal psychosis.

Postictal psychosis (PIP), the occurrence of psychotic episodes following a seizure, is a common and serious comorbidity in patients with epilepsy. Yet, the anatomical correlates remain poorly defined. Here, we used quantitative MRI morphometry to identify structural abnormalities in the cortex of patients with PIP relative to patients with epilepsy without PIP and age- and gender-matched normal healthy controls. Comparison of patients with epilepsy and PIP with patients with epilepsy without PIP revealed increased cortical thickness in the right lateral prefrontal cortex, right anterior cingulate cortex, and right middle temporal gyrus. The PIP group was distinguished from the EC and NC groups by thicker cortex in the right rostral anterior cingulate cortex and thinner cortex in the right angular gyrus and the left middle temporal region. Findings indicate that PIP is associated with thickening of the right anterior cingulate cortex, which may serve as a marker for patients at risk for developing PIP.

Hyperfamiliarity for faces.

OBJECTIVE: To report 4 cases of hyperfamiliarity for faces (HFF) and review 5 previously reported cases. METHODS: We identified cases of HFF from PubMed search and references in prior reports. RESULTS: Three of our 4 cases had pathologic findings that were most extensive in the left temporal lobe. HFF occurred after a tonic-clonic seizure (cases 1 and 3), during simple partial seizures (case 2), and in the setting of an increase in simple partial seizure frequency but not during seizures (case 4). All 9 cases were adults with 1 or more seizures; symptoms first occurred after seizures in 5 cases and during seizures in 1 case. Ictal symptoms lasted from seconds to minutes and from 2 days to more than 7 years in the other 6 cases. The duration of HFF was not associated with the presence or extent of a structural lesion. While in several cases HFF appears to result from a postictal Todd paralysis, the mechanism underlying persistent cases is uncertain. CONCLUSIONS: This modality (visual)-specific and stimulus (face)-specific syndrome is associated with diverse structural, functional imaging, and neurophysiologic findings. Lesions are more often left-sided and involve the temporal lobe. Epilepsy and seizures were present in all 9 cases, suggesting a pathophysiologic relationship, which likely varies among cases. Although only reported in 9 patients, HFF is probably much more common than it is diagnosed.

Auditory-visual processing represented in the human superior temporal gyrus.

In natural face-to-face communication, speech perception utilizes both auditory and visual information. We described previously an acoustically responsive area on the posterior lateral surface of the superior temporal gyrus (field PLST) that is distinguishable on physiological grounds from other auditory fields located within the superior temporal plane. Considering the empirical findings in humans and non-human primates of cortical locations responsive to heard sounds and/or seen sound-sources, we reasoned that area PLST would also contain neural signals reflecting audiovisual speech interactions. To test this hypothesis, event related potentials (ERPs) were recorded from area PLST using chronically implanted multi-contact subdural surface-recording electrodes in patient-subjects undergoing diagnosis and treatment of medically intractable epilepsy, and cortical ERP maps were acquired during five contrasting auditory, visual and bimodal speech conditions. Stimulus conditions included consonant-vowel (CV) syllable sounds alone, silent seen speech or CV sounds paired with a female face articulating matched or mismatched syllables. Data were analyzed using a MANOVA framework, with the results from planned comparisons used to construct cortical significance maps. Our findings indicate that evoked responses recorded from area PLST to auditory speech stimuli are influenced significantly by the addition of visual images of the moving lower face and lips, either articulating the audible syllable or carrying out a meaningless (gurning) motion. The area of cortex exhibiting this audiovisual influence was demonstrably greater in the speech-dominant hemisphere.

Age-related changes in olfactory processing detected with olfactory event-related brain potentials using velopharyngeal closure and natural breathing.

Previous olfactory event-related potential (OERP) studies often employed the Velopharyngeal Closure (VC) method, which prevents respiratory air flow in the nose during odor presentation. However, the use of VC has limited the application of OERPs to populations able to perform this artificial breathing technique. The present study investigated the effects of Natural Breathing (NB) in comparison to VC on OERP latency and amplitude in young (mean age: 24 years) and elderly (mean age: 71 years) adults. OERPs were recorded from three midline scalp electrodes (Fz, Cz, Pz) for 15 trials in each breathing condition with an interstimulus interval of 3.5 min, using amyl-acetate as stimulus. Subjects were asked to report perceived stimulus intensity. A thermistor placed inside one nostril monitored nasal respiration and performance of VC. In the NB condition, subjects were instructed to breathe normally through mouth and nose, while stimulus presentation occurred during inspiration. In both breathing conditions, elderly subjects showed significantly smaller N1-P2 and N1-P3 interpeak amplitudes and longer latencies for N1, P2, P3 than younger subjects. VC generated significantly larger N1-P2 amplitudes across all electrode sites, whereas Natural Breathing produced a trend towards shorter P3 latencies. No significant interaction was found between age and breathing technique. The present investigation showed that the OERP is a sensitive measure for detecting age-related changes in olfactory function regardless of breathing technique.