Neuroscience
-
The behavioral, cognitive, and sensory difficulties experienced by individuals exposed to alcohol prenatally currently fail to provide early identification for fetal alcohol spectrum disorder (FASD). Attempting to advance this pursuit through a multivariate analysis, we collected magnetoencephalography (MEG) data during auditory, somatosensory, visual paradigms, DTI, and behavior in adolescents ages 12-21 years (FASD: N = 13; HC: N = 20). We assessed the relationship between brain function (MEG) and structure (fractional anisotropy (FA)) utilizing joint independent component analysis (jICA), and examined how this measure relates to behavior. ⋯ Interestingly, this relationship is lacking in FASD (r = 0.009, p = 0.979). Also, component 5 loading factor negatively correlated with impulsivity (r = -0.527, p = 0.002), indicating that stronger function-structure associations were associated with individuals with lower impulsivity. These findings suggest that multimodal integration of MEG and FA provides novel associations between structure and function that may help differentiate adolescents with FASD from HC.
-
The theory of communication through coherence (CTC) posits the synchronization of brain oscillations as a key mechanism for information sharing and perceptual binding. In a parallel literature, hippocampal theta activity (4-10 Hz) has been shown to modulate the appearance of neocortical fast gamma oscillations (100-150 Hz), a phenomenon known as cross-frequency coupling (CFC). Even though CFC has also been previously associated with information routing, it remains to be determined whether it directly relates to CTC. ⋯ To answer this question, we combined CFC (modulation index) and CTC (phase-locking value) metrics in order to detect the modulation of the cross-regional high-frequency synchronization by the phase of slower oscillations. Upon applying this method, we found that the inter-hemispheric synchronization of neocortical fast gamma during REM sleep depends on the instantaneous phase of the theta rhythm. These results show that CFC is likely to aid long-range information transfer by facilitating the synchronization of faster rhythms, thus consistent with classical CTC views.
-
This is the first study to examine the influence of activity in one limb on corticospinal excitability to the contralateral limb during a locomotor output. Corticospinal and spinal excitability to the biceps brachii of the ipsilateral arm were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of corticospinal axons, respectively. Responses were evoked during the mid-elbow extension position of arm cycling across three different cycling tasks: (1) bilateral arm cycling (BL), (2) unilateral, contralateral cycling with the ipsilateral arm moving passively (IP), and (3) unilateral, contralateral cycling with the ipsilateral arm at rest (IR). ⋯ TMES-evoked cervicomedullary MEP (CMEPs) amplitudes followed a similar pattern of task-dependent modulation, with BL having the smallest CMEPs and IR having the largest. In line with our previous findings, MEP amplitudes increased and CMEP amplitudes decreased as the cadence increased from 60 to 90 rpm. We suggest that the higher corticospinal excitability to the ipsilateral limb during the IP and IR conditions was predominantly due to disinhibition at both the cortical and spinal levels.
-
Low-power and high-frequency bidirectional control of spatiotemporal patterns of neural spiking is one of the major challenges in optogenetics. A detailed theoretical analysis and optimization with ChR2-NpHR, ChR2(H134R)-eNpHR3.0, Chrimson-GtACR2 and also with prospective opsin pairs namely, Chronos-Jaws, Chronos-eNpHR3.0, CheRiff-Jaws and vf-Chrimson-GtACR2 has been presented. Biophysical circuit models of bidirectional optogenetic control in above opsin pairs expressing hippocampal neurons and fast-spiking neocortical interneurons have been formulated. ⋯ Although, Chrimson-GtACR2 enables bidirectional control at very low-power, vf-Chrimson-GtACR2 provides control with reduced cross-talk. The theoretical analysis highlights the usefulness of computational methods to virtually optimize stimulation protocols for optogenetic tool combinations. The study is useful to generate neural codes with desired spatiotemporal resolution and to design optogenetic neuroprosthetic devices and circuits.
-
It is well established that task complexity can affect both performance and brain processing. Event-related potentials (ERPs) studies have shown modulation of the well-known N2 and P3 components. However, limited information is available on the recently described frontal components associated with processing within the anterior insular cortex. ⋯ The task comparison revealed enhanced pP1 and pP2 components but a reduced N2 component in the complex paradigm. These results suggest that task complexity may entail greater processing strength in the anterior insula functions associated with endogenous perceptual processing. Also, findings on the N2 activity provide evidence against both the inhibitory and conflict interpretation of this component, as the N2 amplitude was reduced in the complex task.