The mismatch negativity (MMN) potential as a tool for the functional mapping of temporal lobe epilepsies

Neural correlates of novelty detection in the primary auditory cortex of behaving monkeys

The neural mechanisms underlying novelty detection are not well understood, especially in relation to behavior. Here, we present single-unit responses from the primary auditory cortex (A1) from two monkeys trained to detect deviant tones amid repetitive ones. Results show that monkeys can detect deviant sounds, and there is a strong correlation between late neuronal responses (250-350 ms after deviant onset) and the monkeys' perceptual decisions. The magnitude and timing of both neuronal and behavioral responses are increased by larger frequency differences between the deviant and standard tones and by increasing the number of standard tones preceding the deviant. This suggests that A1 neurons encode novelty detection in behaving monkeys, influenced by stimulus relevance and expectations. This study provides evidence supporting aspects of predictive coding in the sensory cortex.

Effects of bumetanide on neurodevelopmental impairments in patients with tuberous sclerosis complex: an open-label pilot study

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant disease that affects multiple organs including the brain. TSC is strongly associated with broad neurodevelopmental disorders, including autism spectrum disorder symptomatology. Preclinical TSC studies have indicated altered neuronal chloride homeostasis affecting the polarity of γ-aminobutyric acid (GABA) ergic transmission as a potential treatment target. Bumetanide, a selective NKCC1 chloride importer antagonist, may attenuate depolarizing GABA action, and in that way reduce disease burden. In this open-label pilot study, we tested the effect of bumetanide on a variety of neurophysiological, cognitive, and behavioral measures in children with TSC.

METHODS

Participants were treated with bumetanide (2dd 0.5-1.0 mg) for 13 weeks in an open-label trial. The Aberrant Behavior Checklist-Irritability (ABC-I) subscale was chosen as the primary endpoint. Secondary endpoints included other behavioral questionnaires in addition to event-related potentials (ERP) and neuropsychological tests if tolerated. Additionally, the treatment effect on seizure frequency and quality of life was assessed. Endpoint data were collected at baseline, after 91 days of treatment and after a 28-day wash-out period.

RESULTS

Fifteen patients (8-21-years old) with TSC were included of which 13 patients completed the study. Treatment was well-tolerated with only expected adverse events due to the diuretic effects of bumetanide. Irritable behavior (ABC-I) showed significant improvement after treatment in 11 out of 13 patients (t(12) = 4.41, p = .001, d = .773). A favorable effect was also found for social behavior (Social Responsiveness Scale) (t(11) = 4.01, p = .002, d = .549) and hyperactive behavior (ABC-hyperactivity subscale) (t(12) = 3.65, p = .003, d = .686). Moreover, patients rated their own health-related quality of life higher after treatment. At baseline, TSC patients showed several atypical ERPs versus typically developing peers of which prepulse inhibition was significantly decreased in the TSC group. Neuropsychological measurements showed no change and bumetanide had no effect on seizure frequency.

LIMITATIONS

The sample size and open-label design of this pilot study warrant caution when interpreting outcome measures.

CONCLUSIONS

Bumetanide treatment is a potential treatment to alleviate the behavioral burden and quality of life associated with TSC. More elaborate trials are needed to determine the application and effect size of bumetanide for the TSC population. Trial registration EU Clinical Trial Register, EudraCT 2016-002408-13 (www.clinicaltrialsregister.eu/ctr-search/trial/2016-002408-13/NL). Registered 25 July 2016.

Mismatch negativity is abnormal but not lateralizing in temporal lobe epilepsy

We investigated the changes of mismatch negativity (MMN) in patients with temporal lobe epilepsy (TLE) and explored the possible role of MMN in lateralizing their seizure focus. Thirty patients with TLE and thirty healthy controls were included. MMN was elicited in each subject. Patients with TLE were divided into three subgroups: unilateral left TLE; unilateral right TLE, and bilateral TLE. MMN amplitudes and latencies were compared between the patients with TLE and the control group, and also among the three subgroups of TLE, using repeated measures analyses of variance (ANOVA). To assess the lateralizing value of MMN, MMN latencies and amplitudes at the mastoid sites between the ipsilateral and contralateral sides of epileptic focus in patients with unilateral TLE were compared using t-test. Compared with controls, each subgroup of patients with TLE had longer latencies of MMN at both fronto-central and mastoid sites, but the amplitudes of MMN were not significantly different. The amplitudes and latencies of MMN were not significantly different between the ipsilateral and contralateral sides of seizure focus at mastoid sites. The present findings of prolonged latencies of MMN are suggestive of cognitive impairment in TLE. Both the mastoid sites and the fronto-central sites are involved, which likely reflect widespread cortical abnormalities in TLE. However, the changes of MMN during the interictal phase are not useful for lateralizing the seizure focus in patients with TLE.