Auditory Cortex Represents Both Pitch Judgments and the Corresponding Acoustic Cues

Abstract

SummaryThe neural processing of sensory stimuli involves a transformation of physical stimulus parameters into perceptual features, and elucidating where and how this transformation occurs is one of the ultimate aims of sensory neurophysiology. Recent studies have shown that the firing of neurons in early sensory cortex can be modulated by multisensory interactions [1–5], motor behavior [1, 3, 6, 7], and reward feedback [1, 8, 9], but it remains unclear whether neural activity is more closely tied to perception, as indicated by behavioral choice, or to the physical properties of the stimulus. We investigated which of these properties are predominantly represented in auditory cortex by recording local field potentials (LFPs) and multiunit spiking activity in ferrets while they discriminated the pitch of artificial vowels. We found that auditory cortical activity is informative both about the fundamental frequency (F0) of a target sound and also about the pitch that the animals appear to perceive given their behavioral responses. Surprisingly, although the stimulus F0 was well represented at the onset of the target sound, neural activity throughout auditory cortex frequently predicted the reported pitch better than the target F0.

Cortico‐cortical connectivity within ferret auditory cortex

“…Previous tracer studies in ferret revealed that these areas are innervated by the ventral division of the MGB (Pallas et al, 1990), and that multiple areas, predominantly on the PEG, but also on the AEG, receive connections from the MEG (Wallace and Bajwa, 1991; Pallas and Sur, 1993; Gao and Pallas, 1999). Since these studies were completed, we have gained a deeper understanding of the functional organization of the auditory cortex as assessed by responses to both simple (Kowalski et al, 1995; Nelken et al, 2004; Bizley et al, 2005, 2007a) and complex stimuli (Nelken et al, 2008; Bizley et al, 2009, 2013; Atiani et al, 2014), warranting a more comprehensive investigation of the connectivity within the auditory cortex. Our anatomical investigations support the idea that distinct anterior and posterior processing pathways exist and extend our understanding about the organization of the auditory cortex in the ferret, thus providing crucial information to facilitate cross‐species comparisons.…”

“…The presence of multiple auditory cortical areas on the ectosylvian gyrus (EG) of this species was first demonstrated by using 2‐deoxyglucose autoradiography (Wallace et al, 1997) and subsequently confirmed by using optical imaging of intrinsic signals (Nelken et al, 2004) and single‐unit recording (Kelly et al, 1986; Kelly and Judge, 1994; Kowalski et al, 1995; Bizley et al, 2005). Although most electrophysiological recording studies have focused on the primary auditory cortex (A1) (Phillips et al, 1988; Kowalski et al, 1996; Schnupp et al, 2001; Fritz et al, 2003; Rabinowitz et al, 2011; Keating et al, 2013), the nonprimary auditory fields in this species are now receiving increasing attention (Nelken et al, 2008; Bizley et al, 2009, 2010, 2013; Walker et al, 2011; Atiani et al, 2014). …”

The Contribution of Primary Auditory Cortex to Auditory Categorization in Behaving Monkeys

“…In particular, the specific contributions of the core auditory cortex to perception remain controversial (Binder et al, 2004; Gutschalk et al, 2005; Lemus et al, 2009; Tsunada et al, 2011; Mesgarani and Chang, 2012; Niwa et al, 2012a,b, 2013; Bizley et al, 2013). …”

Neural correlates of auditory streaming in an objective behavioral task

“…For example, analyzing local field potentials in the ferret primary auditory cortex, Bizley et al (36) observed an average area under the ROC curve of up to 0.66 (equivalent to a da value of 0.58) when pooling data from recording sites that significantly represented the information about the stimulus. These authors also compared the area under the choice-derived ROC curves (aROCchoice, indicating the ferrets' decisions) with the area under the stimulus derived ROC curves (aROCstimulus) by a choice index [CI = (aROCchoice -aROCstimulus)/(aROCchoice + aROCstimulus)] and observed a significant positive CI (average, 4.2%) for multiunit activity, indicating that the neurons were slightly more prone to representing the decision rather than the fundamental frequency of the stimulus.…”