Auditory responses from the frontal cortex in the short-tailed fruit bat Carollia perspicillata

Abstract

Based on neuroanatomical findings it was hypothesized that an area in the bat frontal cortex is part of a sensorimotor feedback loop and probably important to goal-directed behaviors guided by auditory information. The present report describes the basic stimulus preferences and response properties of neurons from this area in the short-tailed fruit bat Carollia perspicillata. Responses to acoustic stimuli mimicking biosonar pulse-echo (i.e. FM-FM) combinations were found to be facilitated throughout but only rarely exhibited tuning to pulse-echo delay. As opposed to the often sharply delay-tuned FM-FM neurons in the species' auditory cortex, frontal cortical FM-FM neurons seem to be suited for indicating the presence of an insonified object irrespective of its distance and hence are likely to function as novelty detectors and to trigger changes in the bats' orientation behavior.

Modified synaptic dynamics predict neural activity patterns in an auditory field within the frontal cortex

“…The percentage of units which present latencies lower than 20 ms was 10% in the FAF and 22% in the AC. Lower average latencies in FAF neurons have been reported in previous studies (Eiermann & Esser, ). Differences between our latency results and those from previous studies could be due to anaesthesia effects (ketamine–xylazine mixture [this study] versus awake, Eiermann & Esser, ) and/or differences in the acoustic stimuli used for triggering neuronal firing (pure tones [this study] versus FM and click stimuli, Eiermann & Esser, ).…”

“…On the first day of recordings, a small hole was made in the skull using a scalpel blade on the left side of the cortex in the position corresponding to either the AC or the FAF. To locate the FAF, the sulcus anterior (Figure a) was used as landmark following previous studies (Eiermann & Esser, ). To locate the AC, patterns of blood vessels and the position of the pseudocentral sulcus were used as landmarks (Esser & Eiermann, ; Hagemann, Esser, & Kossl, ).…”

“…Localization of the frontal auditory field (FAF) and auditory cortex (AC) in the brain of the bat Carollia perspicillata . (a) Shows a sketch of C. perspicillata 's brain with the location of the two areas studied (modified from Eiermann & Esser, ). On top of (b), parcellation in the AC of C. perspicillata .…”

“…These afferent patterns hint towards the bat FAF as being a part of the prefrontal cortex described in other mammalian species (Goldman‐Rakic & Porrino, ; Kobler et al, ), pointing to a possible executive role in decision‐making and in integrating multiple time‐varying inputs over time. In response to auditory stimuli, previous studies have shown longer response durations and more diverse peak response latencies in FAF neurons than in AC neurons (Eiermann & Esser, ; Kanwal et al, ). One could speculate that the multiple time‐varying inputs arriving to the frontal cortex could result in different physiological properties in the FAF and AC.…”

“…Studies on non‐primate animal models have postulated that prefrontal areas (as a functional block) are not unique to primates, although this idea continues to be controversial (Uylings, Groenewegen, & Kolb, ; Wise, ). In bats, a highly used animal model for auditory studies, a frontal area responsive to sounds has also been described (Eiermann & Esser, ; Kanwal, Gordon, Peng, & Heinz‐Esser, ). This area was defined as the “frontal auditory field” (FAF).…”