The Maturation of Auditory Perception and Learning

There is one class of beneficial experiences that is common to most developing mammals. Sensory and motor skills improve through practice. Virtually every human skill, from walking to aural communication, emerges slowly during development (Sanes & Wolley, 2011). Thus, our lab studies the neural mechanisms that support the emergence of adult perceptual skills (Sarro & Sanes, 2011; Sarro et al. 2015; Caras & Sanes, 2017; Caras & Sanes, 2019).

To explore the neural mechanisms that underpin the maturation of perception and perceptual learning (Caras & Sanes, 2019), we record wirelessly from auditory cortex while animals practice, and improve on, auditory psychometric tasks.

We are also exploring whether gerbils can learn from one another. In fact, our recent work suggests that auditory learning is facilitated by watching a littermate perform the task (Paraouty et al., ARO 2019 Poster), and future work will extend this principle to developing animals.

The Effect of Developmental Hearing Loss on Sensory and Cognitive Processing

At the other extreme, we study how diminished developmental experience, such as a brief period of hearing loss, can impair both sensory processing and skill learning (Buran et al. 2014; Ihlefeld et al. 2016; Caras & Sanes, 2015). For example, animals reared with conductive hearing loss display delayed learning on an amplitude modulation discrimination task, and poorer psychometric thresholds (von Trapp et al. 2017).

By recording wirelessly from auditory cortex as animals perform an amplitude modulation depth detection task, we discovered that hearing loss leads to degraded encoding in auditory cortex neurons (i.e., a sensory deficit), and diminished gain that ordinarily accompanies attention to the task (i.e., a cognitive deficit) (Yao & Sanes, 2018). A similar effect is observed during amplitude modulation rate discrimination (Yao & Sanes, ARO 2019 Poster). These findings suggest that developmental hearing can induce deficits in both sensory and cognitive processing areas.

The Synaptic Properties that Support of Auditory Perception

One general idea is that these behavioral deficits are due, in part, to the permanent changes to synapse function in specific areas of the brain, including auditory cortex. These synaptic deficits can be induced by even a temporary period of hearing loss (Mowery et al. 2015, 2016, 2017), such as occurs in children with chronic middle ear infections. Thus, a primary translational goal of our research is to understand how these cellular properties can be rescued, thereby restoring normal perceptual abilities.

To ask whether hearing loss-induced changes to auditory cortex cellular properties contribute to perceptual deficits, we have explored the effect of rescuing synaptic inhibition. These studies indicate that normal perceptual skills are restored when animals are treated with a GABAergic enhancer during the critical period (Mowery, Caras, et al., 2019).