Neuronal Mechanisms and Transformations Encoding Time-Varying Signals

Sensation in natural environments requires the analysis of time-varying signals. While previous work has uncovered how a signal’s temporal rate is represented by neurons in sensory cortex, in this issue of Neuron, new evidence from Gao et al. (2016) provides insights on the underlying mechanisms

Auditory and visual sequence learning in humans and monkeys using an artificial grammar learning paradigm

Language flexibly supports the human ability to communicate using different sensory modalities, such as writing and reading in the visual modality and speaking and listening in the auditory domain. Although it has been argued that nonhuman primate communication abilities are inherently multisensory, direct behavioural comparisons between human and nonhuman primates are scant. Artificial grammar learning (AGL) tasks and statistical learning experiments can be used to emulate ordering relationships between words in a sentence. However, previous comparative work using such paradigms has primarily investigated sequence learning within a single sensory modality. We used an AGL paradigm to evaluate how humans and macaque monkeys learn and respond to identically structured sequences of either auditory or visual stimuli. In the auditory and visual experiments, we found that both species were sensitive to the ordering relationships between elements in the sequences. Moreover, the humans and monkeys produced largely similar response patterns to the visual and auditory sequences, indicating that the sequences are processed in comparable ways across the sensory modalities. These results provide evidence that human sequence processing abilities stem from an evolutionarily conserved capacity that appears to operate comparably across the sensory modalities in both human and nonhuman primates. The findings set the stage for future neurobiological studies to investigate the multisensory nature of these sequencing operations in nonhuman primates and how they compare to related processes in humans

Temporal context-guided memory capabilities in rodents

\ua9 The Author(s) 2025. Environmental contexts serve as powerful cues for episodic memory, allowing humans to recall events tied to specific settings. While rats can learn context-specific associations and temporal order, their ability to manage multiple contexts and rapidly adapt to changes in context remains unclear. This study investigated whether rats could order objects across two distinct contexts. Eight Lister Hooded rats were trained in a dual-context maze, where each context contained a pair of objects. In each trial, rats entered the maze, selected an object, and then re-entered either the same or a different context to complete the trial in the correct temporal order. Six rats successfully learned object order within a single context, but only two reached criterion in the more complex two-context condition. Group error analyses revealed a partial reliance on a procedural learning strategy and a tendency to favour one context, where prior location influenced object selection in subsequent trials. While two rats successfully adapted to the two-context condition beyond these simple strategies, most struggled with context switching, exhibiting perseveration difficulties—a trait also observed in some humans. These findings highlight the evolutionary foundations of context-guided memory and reveal remarkable individual variability in the ability to flexibly navigate multiple contexts

Continued need for non-human primate neuroscience research

\ua9 2018 Elsevier Ltd Neuroscience research in non-human primates (NHPs) has delivered fundamental knowledge about human brain function as well as some valuable therapies that have improved the lives of human patients with a variety of brain disorders. Research using NHPs, although it is facing serious challenges, continues to complement studies in human volunteers and patients, and will continue to be needed as the burdens of mental health problems and neurodegenerative diseases increase. At the same time, research into the 3Rs is helping to ameliorate the harms experienced by NHPs in experimental procedures, allowing the effective combination of optimal welfare conditions for the NHPs and high quality research. Mitchell et al. outline the benefits of non-human primate research for medicine and argue that the general public in the UK has been misled about the degree to which animals are harmed during research

Hemispheric Asymmetries in Speech Perception: Sense, Nonsense and Modulations

Background: The well-established left hemisphere specialisation for language processing has long been claimed to be based on a low-level auditory specialization for specific acoustic features in speech, particularly regarding 'rapid temporal processing'.Methodology: A novel analysis/synthesis technique was used to construct a variety of sounds based on simple sentences which could be manipulated in spectro-temporal complexity, and whether they were intelligible or not. All sounds consisted of two noise-excited spectral prominences (based on the lower two formants in the original speech) which could be static or varying in frequency and/or amplitude independently. Dynamically varying both acoustic features based on the same sentence led to intelligible speech but when either or both acoustic features were static, the stimuli were not intelligible. Using the frequency dynamics from one sentence with the amplitude dynamics of another led to unintelligible sounds of comparable spectro-temporal complexity to the intelligible ones. Positron emission tomography (PET) was used to compare which brain regions were active when participants listened to the different sounds.Conclusions: Neural activity to spectral and amplitude modulations sufficient to support speech intelligibility (without actually being intelligible) was seen bilaterally, with a right temporal lobe dominance. A left dominant response was seen only to intelligible sounds. It thus appears that the left hemisphere specialisation for speech is based on the linguistic properties of utterances, not on particular acoustic features

Vocal Learning and Auditory-Vocal Feedback

Vocal learning is usually studied in songbirds and humans, species that can form auditory templates by listening to acoustic models and then learn to vocalize to match the template. Most other species are thought to develop vocalizations without auditory feedback. However, auditory input influences the acoustic structure of vocalizations in a broad distribution of birds and mammals. Vocalizations are dened here as sounds generated by forcing air past vibrating membranes. A vocal motor program may generate vocalizations such as crying or laughter, but auditory feedback may be required for matching precise acoustic features of vocalizations. This chapter discriminates limited vocal learning, which uses auditory input to fine-tune acoustic features of an inherited auditory template, from complex vocal learning, in which novel sounds are learned by matching a learned auditory template. Two or three songbird taxa and four or ve mammalian taxa are known for complex vocal learning. A broader range of mammals converge in the acoustic structure of vocalizations when in socially interacting groups, which qualifies as limited vocal learning. All birds and mammals tested use auditory-vocal feedback to adjust their vocalizations to compensate for the effects of noise, and many species modulate their signals as the costs and benefits of communicating vary. This chapter asks whether some auditory-vocal feedback may have provided neural substrates for the evolution of vocal learning. Progress will require more precise definitions of different forms of vocal learning, broad comparative review of their presence and absence, and behavioral and neurobiological investigations into the mechanisms underlying the skills.PostprintPeer reviewe

Unified ethical principles and an animal research ‘Helsinki’ declaration as foundations for international collaboration

Ethical frameworks are the foundation for any research with humans or nonhuman animals. Human research is guided by overarching international ethical principles, such as those defined in the Helsinki Declaration by the World Medical Association. However, for nonhuman animal research, because there are several sets of ethical principles and national frameworks, it is commonly thought that there is substantial variability in animal research approaches internationally and a lack of an animal research ‘Helsinki Declaration’, or the basis for one. We first overview several prominent sets of ethical principles, including the 3Rs, 3Ss, 3Vs, 4Fs and 6Ps. Then using the 3Rs principles, originally proposed by Russell & Burch, we critically assess them, asking if they can be Replaced, Reduced or Refined. We find that the 3Rs principles have survived several replacement challenges, and the different sets of principles (3Ss, 3Vs, 4Fs and 6Ps) are complementary, a natural refinement of the 3Rs and are ripe for integration into a unified set of principles, as proposed here. We also overview international frameworks and documents, many of which incorporate the 3Rs, including the Basel Declaration on animal research. Finally, we propose that the available animal research guidance documents across countries can be consolidated, to provide a similar structure as seen in the Helsinki Declaration, potentially as part of an amended Basel Declaration on animal research. In summary, we observe substantially greater agreement on and the possibility for unification of the sets of ethical principles and documents that can guide animal research internationally

Exaggerated perception of change with greater sensory imprecision

\ua9 The Author(s) 2025. Bayesian models describe precision (inverse variance) as a key determinant of perception. However, there is limited evidence on the behavioural effects of precision. The default assumption is that higher precision leads to greater surprise (or perceived change) from otherwise equivalent sensory changes. Four human experiments investigated the influence of precision on perceived salience of systematic changes in auditory stimulus streams. Participants reported Perceived Salience of Change (PSC) in the mean value of Gaussian sequences of pure tones varying in either frequency or intensity, with sequences differing in precision. We hypothesised that PSC, for a particular absolute mean change, would positively correlate with stimulus precision. Surprisingly, we observed multiple instances of the opposite effect, where PSC was rated as higher in low-precision conditions. The conditions under which we found evidence for a counter-Bayesian strategy was under extreme values of individual stimuli within sequences, and mostly in experiments where frequency rather than intensity was the varied parameter. Further scrutiny of the specific conditions for these surprising results showed that low precision could be associated with worsened, unaffected or improved correct reporting of the direction of sound frequency change. These results raise the intriguing possibility that certain circumstances, particularly those characterised by low signal-to-noise, human perception may adopt a counter-Bayesian strategy, and we discuss the potential mechanisms, evolutionary benefits, and clinical implications for future work to further test this falsifiable hypothesis

Study of hadronic event-shape variables in multijet final states in pp collisions at √s=7 TeV

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