Experience dependent plasticity alters cortical synchronization

Abstract

Theories of temporal coding by cortical neurons are supported by observations that individual neurons can respond to sensory stimulation with millisecond precision and that activity in large populations is often highly correlated. Synchronization is highest between neurons with overlapping receptive fields and modulated by both sensory stimulation and behavioral state. It is not yet clear whether cortical synchronization is an epiphenomenon or a critical component of efficient information transmission. Experimental manipulations that generate receptive field plasticity can be used to test the relationship between synchronization and receptive fields. Here we demonstrate that increasing receptive field size in primary auditory cortex by repeatedly pairing a train of tones with nucleus basalis (NB) stimulation increases synchronization, and decreasing receptive field size by pairing different tone frequencies with NB stimulation decreases synchronization. These observations seem to support the conclusion that neural synchronization is simply an artifact caused by common inputs. However, pairing tone trains of different carrier frequencies with NB stimulation increases receptive field size without increasing synchronization, and environmental enrichment increases synchronization without increasing receptive field size. The observation that receptive fields and synchronization can be manipulated independently suggests that common inputs are only one of many factors shaping the strength and temporal precision of cortical synchronization and supports the hypothesis that precise neural synchronization contributes to sensory information processing.

Vagus nerve stimulation modulates cortical synchrony and excitability through the activation of muscarinic receptors

“…Recordings were made in an electrically shielded sound-attenuating chamber and sounds were presented in free field via a calibrated speaker (sigcal software and FF1 speaker, Tucker-Davis Technologies). Cross-correlation functions were computed for each recording pair (grouped by cortical separation) by counting the number of spike coincidences of the two clusters for various time shifts (Ϫ50 to 50 ms) between the two spike trains (1 ms bin size) and normalized by dividing each of its bins by the square root of the product of the number of discharges in both spike trains (Kilgard et al, 2007). Because multi-unit data were used, no assumptions are made on neural connectivity.…”

Consequences of unilateral hearing loss: Cortical adjustment to unilateral deprivation

“…Furthermore, neurons in auditory cortex alter their response properties subsequent to changes in stimulus pairings involved in learning and attention paradigms (e.g., Recanzone et al, 1993;Kilgard et al, 2007;Weinberger, 2007;Zatorre, 2007).…”

Auditory training of speech recognition with interrupted and continuous noise maskers by children with hearing impairment

“…Perhaps a greater achievement could have been achieved in the interrupted noise condition with a more challenging training task by providing more severe SNR, a larger SNR step-size, or an increase in the number of keywords to recall. Previous researchers have reported the greatest benefit from a perceptual-learning task occurs when training is at a challenging level (Atienza et al, 2002;Kilgard et al, 2007;Moucha and Kilgard, 2006;Tremblay, 2007). Burk and Humes (2008) provided evidence that using lexically-hard words in auditory training in noise was beneficial for improving speech recognition in noise for adults with HI.…”

“…The auditory training paradigm was designed to adapt to the individual's performance across several levels. This type of perceptual training has been successful in examining neural and behavioral changes in animals and humans (Alain and Tremblay, 2007;Atienza et al, 2002;Boothroyd, 2010;Kilgard et al, 2007;Moucha and Kilgard, 2006;Tremblay et al, 1997;Tremblay et al, 1998). Auditory training in noise resulted in improved speech recognition in noise for adults with HI and in some instances led to a generalization of improvements to novel stimuli (Burk and Humes, 2008;Sweetow and Sabes, 2006).…”