Increased activation of the human cerebellum during pitch discrimination: a positron emission tomography (PET) study.

Recent years have seen a growing debate concerning the function of the cerebellum. Here we used a pitch discrimination task and PET to test for cerebellar involvement in the active control of sensory data acquisition. Specifically, we predicted greater cerebellar activity during active pitch discrimination compared to passive listening, with the greatest activity when pitch discrimination was most difficult. Ten healthy subjects were trained to discriminate deviant tones presented with a slightly higher pitch than a standard tone, using a Go/No Go paradigm. To ensure that discrimination performance was matched across subjects, individual psychometric curves were assessed beforehand using a two-step psychoacoustic procedure. Subjects were scanned while resting in the absence of any sounds, while passively listening to standard tones, and while detecting deviant tones slightly higher in pitch among these standard tones at four different performance levels. Consistent with our predictions, 1) passive listening alone elicited cerebellar activity (lobule IX), 2) cerebellar activity increased during pitch discrimination as compared to passive listening (crus I and II, lobules VI, VIIB, and VIIIB), and 3) this increase was correlated with the difficulty of the discrimination task (lobules V, VI, and IX). These results complement recent findings showing pitch discrimination deficits in cerebellar patients (Parsons et al., 2009) and further support a role for the cerebellum in sensory data acquisition. The data are discussed in the light of anatomical and physiological evidence functionally connecting auditory system and cerebellum.

Physiological correlates and emotional specificity of human piloerection.

Piloerection is known as an indicator of strong emotional experiences. However, little is known about the physiological and emotional specificity of this psychophysiological response. In the presented study, piloerection was elicited by audio stimuli taken from music and film episodes. The physiological response accompanying the incidence of piloerection was recorded with respect to electrodermal, cardiovascular and respiratory measures and compared to a matched control condition. The employment of an optical recording system allowed for a direct and objective assessment of visible piloerection. The occurrence of piloerection was primarily accompanied by an increase of phasic electrodermal activity and increased respiration depth as compared to a matched control condition. This physiological response pattern is discussed in the context of dominant theories of human piloerection. Consideration of all available evidence suggests that emotional piloerection represents a valuable indicator of the state of being moved or touched.

Echoic memory in pigeons.

It is unknown whether birds are able to retain the memory of purely sensory auditory information such as white noise over an extended period of time. In a Pavlovian heart rate conditioning paradigm, four pigeons were trained to associate a mild electric shock with periodic random waveforms, and no shock with aperiodic noise. Periodic waveform detection requires echoic memory, i.e., the online retention of a waveform pattern over a limited time. Starting with 40ms, the waveform period was increased after successful learning until no significant stimulus discrimination could be found. Significant discrimination was achieved at periods of up to 2560ms. This is the first demonstration that echoic memory performance in birds is clearly superior to cats and gerbils, and comparable to naive human performance.

Auditory sensory memory for random waveforms in the Mongolian gerbil.

Mongolian gerbils (N = 21) were trained to discriminate between continuous and repeated auditory white noise. While for periods up to 40 ms of the repeated noise spectral effects make this a perceptual task, longer periods require auditory sensory memory to solve the task. Short periods (20 ms) could easily be discriminated by naive gerbils (discrimination performance, i.e. hit rate minus false alarm rate >80% after 8 days of training). Discrimination was more difficult for longer periods (100 ms: discrimination performance approximately 50% after 18 days of training). By long-term training (156 days) using an optimized training paradigm two further gerbils learned to discriminate up to a period length of 360 ms but could not proceed at 400 ms. While this falls short of human performance, it demonstrates for the first time sensory memory for random waveforms in animals.