Online experimental platforms can be used as an alternative to, or complement, lab-based research. However, when conducting auditory experiments via online methods, the researcher has limited control over the participants’ listening environment. We offer a new method to probe one aspect of that environment, headphone use. Headphones not only provide better control of sound presentation but can also “shield” the listener from background noise. Here we present a rapid (< 3 min) headphone screening test based on Huggins Pitch (HP), a perceptual phenomenon that can only be detected when stimuli are presented dichotically. We validate this test using a cohort of “Trusted” online participants who completed the test using both headphones and loudspeakers. The same participants were also used to test an existing headphone test (AP test; Woods et al., 2017, Attention Perception Psychophysics). We demonstrate that compared to the AP test, the HP test has a higher selectivity for headphone users, rendering it as a compelling alternative to existing methods. Overall, the new HP test correctly detects 80% of headphone users and has a false-positive rate of 20%. Moreover, we demonstrate that combining the HP test with an additional test–either the AP test or an alternative based on a beat test (BT)–can lower the false-positive rate to ~ 7%. This should be useful in situations where headphone use is particularly critical (e.g., dichotic or spatial manipulations). Code for implementing the new tests is publicly available in JavaScript and through Gorilla (gorilla.sc).

Online experimental platforms can be used as an alternative, or complement, to lab-based research. However, when conducting auditory experiments via online methods, the researcher has limited control over the participants’ listening environment. We offer a new method to probe one aspect of that environment, headphone use. Headphones not only provide better control of sound presentation but can also “shield” the listener from background noise. Here we present a rapid (< 3 minute) headphone screening test based on Huggins Pitch (HP), a perceptual phenomenon that can only be detected when stimuli are presented dichotically. We validate this test using a cohort of “Trusted” online participants who completed the test using both headphones and loudspeakers. The same participants also trialled a widely used headphone test (AP test; Woods et al., 2017). We demonstrate that compared to the AP test, the HP test has a higher selectively for headphone users, rendering it as a compelling alternative to the existing screening method. Overall, the new HP test correctly detects 80% of headphone users and has a false positive rate of 20%. Moreover, we demonstrate that there is little overlap between participants who pass both HP and AP tests over loudspeakers. Therefore, combining the two tests can lower the false positive rate to ~7% (but at the expense of an increased false negative rate). This should be useful in situations where headphone use is particularly critical (e.g. dichotic or spatial manipulations). An implementation of the new test is available with JavaScript and through Gorilla (gorilla.sc).

No abstract

The cochlea decomposes sounds into separate frequency channels, from which the auditory brain must reconstruct the auditory scene. To do this the auditory system must make decisions about which frequency information should be grouped together, and which should remain distinct. Two key cues for grouping are temporal coherence, resulting from coherent changes in power across frequency, and temporal predictability, resulting from regular or predictable changes over time. To test how these cues contribute to the construction of a sound scene we present listeners with a range of precursor sounds, which act to prime the auditory system by providing information about each sounds structure, followed by a fixed masker in which participants were required to detect the presence of an embedded tone. By manipulating temporal coherence and/or temporal predictability in the precursor we assess how prior sound exposure influences subsequent auditory grouping. In Experiment 1, we measure the contribution of temporal predictability by presenting temporally regular or jittered precursors, and temporal coherence by using either narrow or broadband sounds, demonstrating that both independently contribute to masking/unmasking. In Experiment 2, we measure the relative impact of temporal coherence and temporal predictability and ask whether the influence of each in the precursor signifies an enhancement or interference of unmasking. We observed that interfering precursors produced the largest changes to thresholds.

Ferrets (Mustela putorius furo) are a valuable animal model used in biomedical research. Like many animals, ferrets undergo significant variation in body weight seasonally, affected by photoperiod, and these variations complicate the use weight as an indicator of health status. To overcome this requires a better understanding of these seasonal weight changes. We provide a normative weight data set for the female ferret accounting for seasonal changes, and also investigate the effect of fluid regulation on weight change. Female ferrets (n = 39) underwent behavioural testing from May 2017 to August 2019 and were weighed daily, while housed in an animal care facility with controlled light exposure. In the winter (October to March), animals experienced 10 hours of light and 14 hours of dark, while in summer (March to October), this contingency was reversed. Individual animals varied in their body weight from approximately 700 to 1200 g. However, weights fluctuated with light cycle, with animals losing weight in summer, and gaining weight in winter such that they fluctuated between approximately 80% and 120% of their long-term average. Ferrets were weighed as part of their health assessment while experiencing water regulation for behavioural training. Water regulation superimposed additional weight changes on these seasonal fluctuations, with weight loss during the 5-day water regulation period being greater in summer than winter. Analysing the data with a Generalised Linear Model confirmed that the percentage decrease in weight per week was relatively constant throughout the summer months, while the percentage increase in body weight per week in winter decreased through the season. Finally, we noted that the timing of oestrus was reliably triggered by the increase in day length in spring. These data establish a normative benchmark for seasonal weight variation in female ferrets that can be incorporated into the health assessment of an animal's condition.

A key question in auditory neuroscience is to what extent are brain regions functionally specialized for processing specific sound features such as location and identity. In auditory cortex, correlations between neural activity and sounds support both the specialization of distinct cortical subfields, and encoding of multiple sound features within individual cortical areas. However, few studies have tested the contribution of auditory cortex to hearing in multiple contexts. Here we determined the role of ferret primary auditory cortex in both spatial and non-spatial hearing by reversibly inactivating the middle ectosylvian gyrus during behavior using cooling (n=2 females) or optogenetics (n=1 female). Optogenetic experiments utilized the mDLx promoter to express Channelrhodopsin2 in GABAergic interneurons and we confirmed both viral expression (n=2 females) and light-driven suppression of spiking activity in auditory cortex, recorded using Neuropixels under anesthesia (n=465 units from 2 additional untrained female ferrets). Cortical inactivation via cooling or optogenetics impaired vowel discrimination in co-located noise. Ferrets implanted with cooling loops were tested in additional conditions that revealed no deficits for identifying vowels in clean conditions, or when the temporally coincident vowel and noise were spatially separated by 180 degrees. These animals did however show impaired sound localization when inactivating the same auditory cortical region implicated in vowel discrimination in noise. Our results demonstrate that, as a brain region showing mixed selectivity for spatial and non-spatial features of sound, primary auditory cortex contributes to multiple forms of hearing.SIGNIFICANCE STATEMENT:Neurons in primary auditory cortex are often sensitive to the location and identity of sounds. Here we inactivated auditory cortex during spatial and non- spatial listening tasks using cooling, or optogenetics. Auditory cortical inactivation impaired multiple behaviors, demonstrating a role in both the analysis of sound location and identity and confirming a functional contribution of mixed selectivity observed in neural activity. Parallel optogenetic experiments in two additional untrained ferrets linked behavior to physiology by demonstrating that expression of Channelrhodopsin 2 permitted rapid light-driven suppression of auditory cortical activity recorded under anesthesia.

21 Ferrets (Mustela putorius furo) are a valuable animal model used in biomedical research.22 Ferrets undergo significant variation in body weight seasonally, affected by photoperiod, 23 and these variations make it difficult to use weight as an indicator of health status. To 24 overcome this requires a better understanding of these seasonal weight changes. We 25 provide a normative weight data set for the female ferret accounting for seasonal 26 changes, and also investigate the effect of fluid regulation on weight change. Female 27 ferrets (n=39) underwent behavioural testing from May 2017 to August 2019 and were 28 weighed daily while housed in an animal care facility with controlled light exposure. In the 29 winter (October to March), animals experienced 10 hours of light and 14 hours of dark, 30 while in summer (March to October), this contingency was reversed. Individual animals 31 varied in their body weight from approximately 700 to 1200 g. However, weights fluctuated 32 with light cycle, with animals losing weight in summer, and gaining weight in winter such 33 that they fluctuated between approximately 80% and 120% of their long term average 34 weight. Ferrets were weighed as part of their health assessment while experiencing water 35 regulation for behavioural training. Water regulation superimposed additional weight 36 changes on these seasonal fluctuations, with weight loss during the 5 day water 37 regulation period being greater in summer than winter. These data establish a normative 38 benchmark for seasonal weight variation in female ferrets that can be incorporated into 39 the health assessment of an animal's condition. 3 40 Introduction 41 Domesticated ferrets (Mustela putorius furo) are valuable animal models for a wide range 42 of biomedical research areas, including: neuroscience [1-6], drug development [7] and 43 respiratory diseases such as Influenza and Severe Acute Respiratory Syndrome (SARS) 44 [ 8,9] including the new coronavirus strain, SARS-CoV-2 [10]. In laboratory animals 45 exposed to scientific procedures, a standard approach to monitoring health status is to 46 measure body weight. Weight loss is a key indicator of health problems, and therefore 47 understanding the factors that contribute to natural variation in body weight is critical for 48 correctly monitoring an animal's condition. Ferrets undergo significant variation in their 49 body weight seasonally; however, there is currently no normative data available to provide 50 a benchmark for the expected seasonal weight changes. Seasonal variations may mask 51 or exaggerate changes in body weight due to an experimental procedure or change in 52 health status and thus must be integrated into assessments of a ferret's health status. 53Seasonal weight changes have been demonstrated in multiple species 54 independent of diurnality, including monkeys [11,12], raccoons [13], hamsters [14] and 55 rodents [15]. There are a range of potential factors that elicit seasonal weight changes, 56 but temperature and day length are key trigge...

A key question in auditory neuroscience is how far brain regions are functionally specialized for processing specific sound features such as sound location and identity. In auditory cortex, correlations between neural activity and sounds support both the specialization of distinct cortical subfields, and encoding of multiple sound features within individual cortical areas. However, few studies have tested the causal contribution of auditory cortex to hearing in multiple contexts. Here we tested the role of auditory cortex in both spatial and non-spatial hearing. We reversibly inactivated the border between middle and posterior ectosylvian gyrus using cooling (n=2) or optogenetics (n=1) as ferrets discriminated vowel sounds in discriminated vowel sounds in noise. Animals with cooling loops were also presented with vowels in clean conditions, and then retrained to localize noise-bursts from multiple locations and tested with cooling. Cortical inactivation impaired sound localization and vowel discrimination in noise, but not discrimination in clean conditions. We also tested the effects of cooling on vowel discrimination in noise when vowel and noise were colocated or spatially separated. Here, cooling impaired discriminating vowels with colocalized but not spatially separated noise, such that we could observe spatial release from masking during cortical inactivation. Together our results show that auditory cortex contributes to both spatial and non-spatial hearing, consistent with single unit recordings in the same brain region. The deficits we observed did not reflect general impairments in hearing, but rather are consistent with a role for auditory cortex in auditory scene analysis.