Owing to their simplicity, STRFs can be reliably estimated by using randomly chosen structured stimuli, such as ripplesħ, and relatively small amounts of data. Most widely used as part of a linear-nonlinear (LN) model, an STRF comprises a set of coefficients that describe how the response of the neuron at each moment in time can be modelled as a linear weighted sum of the recent history of the stimulus power in different spectral channels. The spectrotemporal receptive fieldĤ (STRF) is the dominant computational tool for characterizing the responses of auditory neurons. Reflecting the spectral analysis that begins in the inner ear, auditory neurons are most commonly characterized by their sensitivity to sound frequency. The tuning properties of sensory neurons are defined by their receptive fields, which describe the stimulus features to which they are most responsive. Finally, we look at the cognitive role of auditory cortex, highlighting its involvement in prediction, learning, and decision making. Second, we examine the distribution of those stimulus preferences within A1 and across the hierarchy of auditory cortical areas, focusing on the extent to which this conforms to canonical principles of columnar organization and functional specialization that are the hallmark of visual and somatosensory processing. First, we consider what sound features A1 neurons represent, highlighting recent attempts to improve receptive field models that can predict the responses of neurons to natural sounds. In this review, we focus on three key areas of auditory cortical processing where there has been progress in the last few years. The auditory cortex is therefore an integral part of the network of brain regions responsible for generating meaning from sounds, auditory perceptual decision-making, and learning. Equally important is the growing realization that auditory cortical processing, in particular, is highly context-dependent and integrates auditory (and other sensory) inputs with information about an individual’s current internal state, including their arousal level, focus of attention, and motor planning, as well as their past experienceĢ. Although this partly reflects the emergence of response properties, such as sensitivity to combinations of sound features, it is striking how similar many of the properties of neurons in the primary auditory cortex (A1) are to those of subcortical neuronsġ. It is widely thought to be the case, however, that the auditory cortex plays a critical role in the perception of complex sounds. Many aspects of hearing-such as computation of the cues that enable sound sources to be localized or their pitch to be extracted-rely on the processing that takes place in the brainstem and other subcortical structures. Our seemingly effortless ability to localize, distinguish, and recognize a vast array of natural sounds, including speech and music, results from the neural processing that begins in the inner ear and continues through a complex sequence of subcortical and cortical brain areas. In this review, we focus on three key areas that are contributing to this understanding: the sound features that are preferentially represented by cortical neurons, the spatial organization of those preferences, and the cognitive roles of the auditory cortex. Thus, in addition to being the locus for more complex sound selectivity, the auditory cortex is increasingly understood to be an integral part of the network of brain regions responsible for prediction, auditory perceptual decision-making, and learning. Furthermore, recent work has shown that auditory cortical processing is highly context-dependent, integrates auditory inputs with other sensory and motor signals, depends on experience, and is shaped by cognitive demands, such as attention. Although many of the properties of neurons in the auditory cortex resemble those of subcortical neurons, they show somewhat more complex selectivity for sound features, which is likely to be important for the analysis of natural sounds, such as speech, in real-life listening conditions. The specific contribution of the auditory cortex to this chain of processing is far from understood. Our ability to make sense of the auditory world results from neural processing that begins in the ear, goes through multiple subcortical areas, and continues in the cortex.
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