Positive impacts of early auditory training on cortical processing at an older age

Abstract

Progressive negative behavioral changes in normal aging are paralleled by a complex series of physical and functional declines expressed in the cerebral cortex. In studies conducted in the auditory domain, these degrading physical and functional cortical changes have been shown to be broadly reversed by intensive progressive training that improves the spectral and temporal resolution of acoustic inputs and suppresses behavioral distractors. Here we found older rats that were intensively trained on an attentionally demanding modulation-rate recognition task in young adulthood substantially retained training-driven improvements in temporal rate discrimination abilities over a subsequent 18-mo epoch-that is, forward into their older age. In parallel, this young-adult auditory training enduringly enhanced temporal and spectral information processing in their primary auditory cortices (A1). Substantially greater numbers of parvalbumin-and somatostatin-labeled inhibitory neurons (closer to the numbers recorded in young vigorous adults) were recorded in the A1 and hippocampus in old trained versus untrained age-matched rats. These results show that a simple form of training in young adulthood in this rat model enduringly delays the otherwise expected deterioration of the physical status and functional operations of the auditory nervous system, with evident training impacts generalized to the hippocampus.aging | auditory cortex | behavioral training | cortical processing | inhibition A degradation of the status of physical brain machinery, expressed by a decline in its temporal processing abilities, has been repeatedly associated with its deteriorating functional status in normal aging (1-4). Recent studies have shown that the machinery that supports processing accuracy and speed, as well as the processes supporting attention control and distractor suppression, can be substantially rejuvenated via simple forms of intensive training in the aged-rat model (4, 5). With auditory perceptual training, in parallel with recovery in behavioral abilities to that matching young-animal performance levels, serials of key physical, chemical, and functional aspects of cortical processing machinery in the trained rats were shown to be restored to a physical or functional status that approached that normally recorded in vigorous young-adult animals.In human studies, substantial changes in speed of processing (SOP) and in other spectro-temporal (or spatiotemporal) signal resolution of performance abilities have been shown to result from attention-demanding, speed-challenged auditory (3, 5-7) or visual training (8-11). For example, the accurate behavioral identification and stimulus-order reconstruction of rapidly successive auditory stimuli was restored in human individuals trained in their eighth decade of life to a performance level normally typifying human performance abilities recorded in their third or fourth decade (3, 6).Our goal here was to define the magnitude and endurance of an intense dose of attention-demanding modulation di...

The effects of aging on auditory cortical function

“…Importantly, both the physiological responses and anatomical changes were reversed in animals that underwent a training period, indicating that these central changes are not permanent. This finding is consistent with human auditory training paradigms, where different listening tasks can result in both improvements in auditory temporal processing tasks as well as the electrophysiological correlates of brainstem and midbrain responses (Anderson et al, 2013, 2014, Merzenich et al, 2014; Cheng et al, 2017). Thus, while aging can result in rather dramatic physiological and neuroanatomical changes throughout the central nervous system, these particular changes, at least to some degree, appear to be plastic and malleable throughout life.…”

Acoustical Enrichment during Early Development Improves Response Reliability in the Adult Auditory Cortex of the Rat

“…This fact may relate to the experimental paradigm in which the enriched animals were motivated to discriminate several similar stimuli to obtain a reward. Smaller van Rossum distances after an acoustic training have also been observed by Cheng et al [ 19 ].…”

“…It thus appears that the environmental conditions during the critical period of development also influence the properties of the synaptic transmission. As learning, training, and attention were shown to affect neural synchrony [ 19 , 51 ] and modulate neural coding of attended stimuli [ 52 ], the stimulus discrimination task which was included in the enriching environment of the current study probably also contributed to the presented results.…”

“…In addition, the FM tones and click trains were used to determine the similarity of spike trains evoked by the same stimulus. The van Rossum distance [ 18 , 19 ] was computed for each pair of responses of the same neuron to the same stimulus. The van Rossum distance quantifies the similarity of two spike trains X ( k ) and Y ( k ) and is computed as follows: first, each discrete spike train is transformed to continuous function x ( t ) and y ( t ), respectively, using convolution of the spike train with exponential function.…”

Early impoverished environment delays the maturation of cerebral cortex

“…The complexity of early stimulation can modulate brain developmental trajectories and can induce long-term changes in neural circuits that underlie enduring modifications in brain structure and function 1 , 2 . Environmental enrichment (EE) strongly accelerates the maturation of sensory systems 3 – 10 , acting on molecular factors involved in cerebral cortex development and plasticity such as insulin-like growth factor 1 (IGF-1), brain-derived neurotrophic factor (BDNF) and GABAergic transmission 3 , 4 , 11 – 16 . Interestingly, an enriched experience restricted to the pre-weaning period is already sufficient to influence brain development 4 , 17 and contributes to shape inter-individual differences in stress vulnerability and anxiety-like behavior with IGF-1 standing out as a crucial early EE mediator 4 , 17 , 18 .…”