Extensive trial-to-trial variability is a hallmark of most behavioral, cognitive, and physiological processes. Spontaneous brain activity (SBA), a ubiquitous phenomenon that coordinates levels and patterns of neuronal activity throughout the brain, may contribute to this variability by dynamically altering neuronal excitability. In freely-behaving male rats, we observed extensive variability of...

Cortical potentials following sensory stimulation are widely analyzed as the linear combination of an invariant evoked response component, time-locked to the stimulus, and an independent, ongoing noise component. We consider two alternative models and compare their predictions with data. In the "rst model, neuronal populations coupled through nonlinear sigmoid functions have their e!ective conn...

The high variability of cortical sensory responses is often assumed to impose a major constraint on efficient computation. In the auditory cortex, however, response variability can be very low. We have used in vivo whole cell patch-clamp methods to study the trial-to-trial variability of the subthreshold fluctuations in membrane potential underlying tone-evoked responses in the auditory cortex ...

A widely held assumption is that spontaneous and task-evoked brain activity sum linearly, such that the recorded brain response in each single trial is the algebraic sum of the constantly changing ongoing activity and the stereotypical evoked activity. Using functional magnetic resonance imaging signals acquired from normal humans, we show that this assumption is invalid. Across widespread cort...

hyperbilirubinemia at neonatal period is one of the major deteriorating factors of the auditory system. if left untreated, it may cause certain cerebral damage. this study aims to evaluate the impact of hyperbilirubinemia on the hearing of neonate. this study was conducted on 35 newborn babies with jaundice (bilirubin more than 20 mg/dl). auditory brainstem response (abr) and transient evoked o...

Cochlear synaptopathy (or hidden hearing loss), due to noise exposure or aging, has been demonstrated in animal models using histological techniques. However, diagnosis of the condition in individual humans is problematic because of (a) test reliability and (b) lack of a gold standard validation measure. Wave I of the transient-evoked auditory brainstem response is a noninvasive electrophysiolo...

BACKGROUND Deficits in attention and cognition are common in schizophrenia. Using an auditory dual-click paradigm, a number of studies have found that, compared with normal controls, patients with schizophrenia show impaired inhibition, or gating, of repeated stimulation as measured by the average P50 evoked response to the second click. Since responses to many trials are collected to study the...

Behavioral and electrophysiological evidences have shown that locus ceruleus (LC) is involved in different tasks including modulation of sensory processing and shift of attention. In the present study, single unit responses of barrel cortical cells was recorded following controlled mechanical displacement of the principal and peripheral vibrissae in adult rats (100 trials of 200 µm deflection f...

We review neural correlates of perceptual and motor decisions, examining whether the time they occupy explains the duration and variability of behavioral reaction times. The location of a salient target is identified through a spatiotemporal evolution of visually evoked activation throughout the visual system. Selection of the target leads to stochastic growth of movement-related activity towar...