Cortical network reorganization guided by sensory input features

Abstract

Sensory experience alters the functional organization of cortical networks. Previous studies using behavioral training motivated by aversive or rewarding stimuli have demonstrated that cortical plasticity is specific to salient inputs in the sensory environment. Sensory experience associated with electrical activation of the basal forebrain (BasF) generates similar input specific plasticity. By directly engaging plasticity mechanisms and avoiding extensive behavioral training, BasF stimulation makes it possible to efficiently explore how specific sensory features contribute to cortical plasticity. This review summarizes our observations that cortical networks employ a variety of strategies to improve the representation of the sensory environment. Different combinations of receptive-field, temporal, and spectrotemporal plasticity were generated in primary auditory cortex neurons depending on the pitch, modulation rate, and order of sounds paired with BasF stimulation. Simple tones led to map expansion, while modulated tones altered the maximum cortical following rate. Exposure to complex acoustic sequences led to the development of combination-sensitive responses. This remodeling of cortical response characteristics may reflect changes in intrinsic cellular mechanisms, synaptic efficacy, and local neuronal connectivity. The intricate relationship between the pattern of sensory activation and cortical plasticity suggests that network-level rules alter the functional organization of the cortex to generate the most behaviorally useful representation of the sensory environment.

Intensive training in adults refines A1 representations degraded in an early postnatal critical period

“…However, these studies once again demonstrate that the adult auditory cortex remains plastic for attended, rewarded stimuli. It has been suggested that the interaction of auditory inputs, neuromodulator release, and top-down influences from higher auditory areas contribute to this learningbased cortical plasticity (20,(47)(48)(49)(50)(51)(52)(53)(54)(55). The fact that passive exposure to the same stimuli, when not reliably coupled to reward, has no measurable effect on frequency selectivity and tonotopicity of A1 in the present study again supports the conclusion that top-down modulation contributes significantly to learning-induced cortical plasticity in the adult brain (20).…”

Perceptual Learning Directs Auditory Cortical Map Reorganization through Top-Down Influences

“…ditioning or neuromodulatory pairing might also be influenced by top-down mechanisms (for review, see Kilgard et al, 2002;Suga and Ma, 2003;Weinberger, 2004). Ultimately, procedures that characterize plasticity using real-time awake recording methods might reveal top-down mechanisms that allow the cortex to switch between different flexible states of information processing according to rapidly changing environmental demands (Edeline et al, 1993;Ohl and Scheich, 1997;Ohl et al, 2001;Fritz et al, 2003Fritz et al, , 2005.…”

“…Task-dependent influences on receptive fields in the primary sensory cortex have only been observed in awake animals and, even then, have only been observed to last for short periods of time. Studies that investigate long-term effects of conditioning on adult cortical map and/or their constituent receptive field organization have generally claimed that receptive field plas-ticity reflects the pattern of bottom-up sensory inputs and their relationship to reinforcement-based neuromodulator release (Ji et al, 2001;Kilgard et al, 2001Kilgard et al, , 2002Weinberger, 2004;Yan and Zhang, 2005). Our understanding of the relative contribution of bottom-up and top-down signals to adult cortical plasticity has remained clouded, however, because nearly every conditioning study has imposed varying attentional demands on subjects presented with varying sensory inputs.…”

Pathophysiology of Stroke Rehabilitation: The Natural Course of Clinical Recovery, Use-Dependent Plasticity and Rehabilitative Outcome

“…In fact, learning on the network level is in large parts dependent on subjectively connoted sensory stimulation (i.e. salient cues) [56, 124]. Nonetheless, several studies have highlighted the positive effects of simple focused repetitive training [125, 126], though not all with positive results [127].…”