Neocortical dynamics during whisker-based sensory discrimination in head-restrained mice

“Such cortico-cortical projection neurons are found in L2/3 as well as in infragranular layers (Aronoff et al., 2010; Chen et al., 2013a) and different types of neuronal pools with distinct projection targets can be identified in vivo with the help of retrograde tracer injections and two-photon…”

“For example, in previous monkey studies recording from different areas (Bastos et al., 2015; Romo and de Lafuente, 2013; Siegel et al., 2015) it was not possible to dissect the neuronal population from each area into different projections, cell types, or even layer specificity.”

“Third, new transgenic mouse lines expressing sensitive calcium indicators (Dana et al., 2014; Madisen et al., 2015) (Bethge et al., 2017) will further facilitate functional imaging of defined subsets of neurons, applied alone or in combination with viral vectors.”

“The results reported here were obtained with variants of either GCaMP6 (Chen et al., 2013b) or Yellow Cameleon (YC) (Horikawa et al., 2010); more recently, application of red-shifted calcium indicators also has become feasible (Bethge et al., 2017; Dana et al., 2016; Pilz et al., 2016).”

“In addition to M1, there may be other top-down effects from frontal cortex onto S1 that may be relevant for detection and discrimination of objects ((Gilbert and Sigman, 2007; Krupa et al., 2004; van Kerkoerle et al., 2017) for”

“…the stability of head-fixed preparations enables to simultaneously record from a large population of neurons, from tens to hundreds of cells (Chen et al., 2013a; Harvey et al., 2012; O'Connor et al., 2013; Peron et al., 2015) to a whole hemisphere (Ferezou et al., 2007; Mohajerani et al., 2013).”

“M2 projections onto sensory areas play a role in sensory discrimination in multiple modalities, e.g. vision (Zhang et al., 2014) or forelimb somato-sensation (Manita et al., 2015).”

“The integration of M1 feedback in S1 presumably is further shaped by polysynaptic circuit motifs involving inhibitory interneurons, such as the disinhibitory circuit implemented by VIP-expressing interneurons (Lee et al., 2013).”

“The rodent whisker-system has become a popular model system for studying tactile information processing due to is neuroethological relevance (Feldmeyer et al., 2013; Petersen, 2007).”

“Similar approaches are also already applied in other species, for example in head-fixed flies (Kim et al., 2017) and stabilized larval zebrafish (Ahrens et al., 2012).”

“1A), first in a go/no-go paradigm (Chen et al., 2013a; Guo et al., 2014b; Huber et al.; O'Connor et al., 2010a), later as a 2AFC task (Guo et al., 2014a; Li et al., 2015).”

“…the stability of head-fixed preparations enables to simultaneously record from a large population of neurons, from tens to hundreds of cells (Chen et al., 2013a; Harvey et al., 2012; O'Connor et al., 2013; Peron et al., 2015) to a whole hemisphere (Ferezou et al., 2007; Mohajerani et al., 2013).”

“to object contacts, which produce sensory signals reaching S1 that are fed forward to M1 (Diamond et al., 2008; Ferezou et al., 2007; Petersen, 2007).”

“Second, the rapid expansion of imaging technologies enabling simultaneous imaging from large field-of-views or across many areas (Chen et al., 2016; Lecoq et al., 2014; Sofroniew et al., 2016; Stirman et al., 2016a) will continue and enable collection of comprehensive data sets of neuronal network representations and…”

“…perceptual learning have been investigated for decades (Mountcastle, 1993; Romo and Salinas, 2003) and a prime role in perception has been assigned to primary sensory areas in the neocortex, which exhibit a strong relationship between psychometric and neurometric curves (Romo and Salinas, 2003).”

“1A), first in a go/no-go paradigm (Chen et al., 2013a; Guo et al., 2014b; Huber et al.; O'Connor et al., 2010a), later as a 2AFC task (Guo et al., 2014a; Li et al., 2015).”

“Third, new transgenic mouse lines expressing sensitive calcium indicators (Dana et al., 2014; Madisen et al., 2015) (Bethge et al., 2017) will further facilitate functional imaging of defined subsets of neurons, applied alone or in combination with viral vectors.”

“Correspondingly, neurons in vibrissal M1 were also found to become more responsive during the whisker sampling period in the pole detection task (Huber et al., 2012).”

“…recent experiments demonstrate that persistent activity in ALM during movement preparation requires concerted activation of thalamic regions (Guo et al., 2017), indicating that an excitatory cross-regional loop encompassing cortical and sub-cortical regions is required for holding relevant…”

“S1 and M1 are reciprocally connected; whereas S1M1 feed-forward projections are somatotopic (Aronoff et al., 2010; Kleinfeld et al., 2002; Mao et al., 2011) M1S1 feedback projections are more diffusive (Aronoff et al., 2010; Veinante and Deschenes, 2003).”

“Fourth, improved microscopy techniques, including holographic methods (Yang et al., 2016) and 3-photon microscopy with novel laser types (Ouzounov et al., 2017), as well as recent advances in the in vivo application of red-shifted calcium indicators (Dana et al., 2016) (Bethge et al., 2017) should…”

“Animals may also learn to adapt their behavioral strategy to optimize detection of the target stimulus, e.g. by restricting whisking to the expected target pole position, thus effectively turning a discrimination task into a ‘detection with distractors’ task (O'Connor et al., 2010a).”

“For example, in previous monkey studies recording from different areas (Bastos et al., 2015; Romo and de Lafuente, 2013; Siegel et al., 2015) it was not possible to dissect the neuronal population from each area into different projections, cell types, or even layer specificity.”

“1A), first in a go/no-go paradigm (Chen et al., 2013a; Guo et al., 2014b; Huber et al.; O'Connor et al., 2010a), later as a 2AFC task (Guo et al., 2014a; Li et al., 2015).”

“Similar approaches are also already applied in other species, for example in head-fixed flies (Kim et al., 2017) and stabilized larval zebrafish (Ahrens et al., 2012).”

“a particular mechanical stimulus that may or may not be predicted by other sensory cues (Kwon et al., 2016; Sachidhanandam et al., 2013).”

“…the stability of head-fixed preparations enables to simultaneously record from a large population of neurons, from tens to hundreds of cells (Chen et al., 2013a; Harvey et al., 2012; O'Connor et al., 2013; Peron et al., 2015) to a whole hemisphere (Ferezou et al., 2007; Mohajerani et al., 2013).”

“M2 projections onto sensory areas play a role in sensory discrimination in multiple modalities, e.g. vision (Zhang et al., 2014) or forelimb somato-sensation (Manita et al., 2015).”

“The rodent whisker-system has become a popular model system for studying tactile information processing due to is neuroethological relevance (Feldmeyer et al., 2013; Petersen, 2007).”

“…the stability of head-fixed preparations enables to simultaneously record from a large population of neurons, from tens to hundreds of cells (Chen et al., 2013a; Harvey et al., 2012; O'Connor et al., 2013; Peron et al., 2015) to a whole hemisphere (Ferezou et al., 2007; Mohajerani et al., 2013).”

“The importance of M1-to-S1 feedback was further demonstrated by imaging distal dendrites of L5 pyramidal neurons in S1, which elicited dendritic calcium signals when whiskers touched the pole at particular positions (Xu et al., 2012).”

“The results reported here were obtained with variants of either GCaMP6 (Chen et al., 2013b) or Yellow Cameleon (YC) (Horikawa et al., 2010); more recently, application of red-shifted calcium indicators also has become feasible (Bethge et al., 2017; Dana et al., 2016; Pilz et al., 2016).”

“population of neurons, from tens to hundreds of cells (Chen et al., 2013a; Harvey et al., 2012; O'Connor et al., 2013; Peron et al., 2015) to a whole hemisphere (Ferezou et al.”

“19 Further progress will likely occur along multiple lines: First, head-fixed behavioral paradigms will further expand, encompassing discrimination in the auditory and visual modalities, even involving touch-screen based perception tasks (Stirman et al., 2016b), as well as higher cognitive tasks.”

“Such cortico-cortical projection neurons are found in L2/3 as well as in infragranular layers (Aronoff et al., 2010; Chen et al., 2013a) and different types of neuronal pools with distinct projection targets can be identified in vivo with the help of retrograde tracer injections and two-photon…”

“Animals may also learn to adapt their behavioral strategy to optimize detection of the target stimulus, e.g. by restricting whisking to the expected target pole position, thus effectively turning a discrimination task into a ‘detection with distractors’ task (O'Connor et al., 2010a).”

“In addition to M1, there may be other top-down effects from frontal cortex onto S1 that may be relevant for detection and discrimination of objects ((Gilbert and Sigman, 2007; Krupa et al., 2004; van Kerkoerle et al., 2017) for V1 of primates).”

“prominent feature of the physical whisker-sandpaper interaction are so-called ‘stick-slip’ events, which occur when the whisker gets caught by a sandpaper grain, is stretched, and then released like a spring (Arabzadeh et al., 2005; Boubenec et al., 2012; Wolfe et al., 2008).”

“…whisker curvature change, from which lateral and axial forces impinging on the whisker follicles can be estimated (Boubenec et al., 2012; O'Connor et al., 2010a; Pammer et al., 2013), and frequency of stick-slip events (Chen et al., 2015; von Heimendahl et al., 2007; Wolfe et al., 2008).”

“Fourth, improved microscopy techniques, including holographic methods (Yang et al., 2016) and 3-photon microscopy with novel laser types (Ouzounov et al., 2017), as well as recent advances in the in vivo application of red-shifted calcium indicators (Dana et al., 2016) (Bethge et al., 2017) should…”

“across several seconds and aid in haptic perception (Knutsen et al., 2006; Mehta et al., 2007; O'Connor et al., 2010b).”

“…whisker curvature change, from which lateral and axial forces impinging on the whisker follicles can be estimated (Boubenec et al., 2012; O'Connor et al., 2010a; Pammer et al., 2013), and frequency of stick-slip events (Chen et al., 2015; von Heimendahl et al., 2007; Wolfe et al., 2008).”

“For example, the psychophysics of monkeys performing a vibrotactile discrimination task was found to be reflected well by the differences in neuronal firing rates in primary somatosensory cortex (S1) (Hernandez et al., 2000).”

“a particular mechanical stimulus that may or may not be predicted by other sensory cues (Kwon et al., 2016; Sachidhanandam et al., 2013).”

“Here, the ability to consistently find the same cells under the two-photon microscope again and again over days to weeks – using anatomical landmarks such as blood vessel pattern and neuronal cell body constellations (Margolis et al., 2012) – is a crucial advantage.”

“Feedback from M1 to S1 is thought to carry information about whisker position (Hill et al., 2011; Petreanu et al., 2012).”

“across several seconds and aid in haptic perception (Knutsen et al., 2006; Mehta et al., 2007; O'Connor et al., 2010b).”

“(A-D) adapted from (Chen et al., 2015).”

“S1S2 and S1M1 projection neurons were shown to differ in their intrinsic electrophysiological properties in vivo (Yamashita et al., 2013).”

“Originally designed for rats (Hill et al., 2008), the rostro-caudal pole localization task was adopted for head-restrained mice”

“carries more information about texture stimuli and choice compared to spike rate (Zuo et al., 2015).”

“…this review, rather than discussing neural correlates of perceptual detection thresholds and discrimination thresholds (for excellent reviews see (Diamond and Arabzadeh, 2013; Romo and de Lafuente, 2013; Romo and Salinas, 2003; Stuttgen et al., 2011), we focus on experimental conditions where…”

“Second, the rapid expansion of imaging technologies enabling simultaneous imaging from large field-of-views or across many areas (Chen et al., 2016; Lecoq et al., 2014; Sofroniew et al., 2016; Stirman et al., 2016a) will continue and enable collection of comprehensive data sets of neuronal network…”

“, 2011) M1S1 feedback projections are more diffusive (Aronoff et al., 2010; Veinante and Deschenes, 2003).”

“activity between these areas, related to both motor behavior (whisking and licking) as well as sensory processing (Chen et al., 2016) (Fig.”

“Finally, head-fixed mice free to navigate on a spherical treadmill use their whiskers can naturally track their position within a virtual corridor built by two opposing walls (Sofroniew et al., 2015) (Fig.”

“S1 and M1 are reciprocally connected; whereas S1M1 feed-forward projections are somatotopic (Aronoff et al., 2010; Kleinfeld et al., 2002; Mao et al., 2011) M1S1 feedback projections are more diffusive (Aronoff et al., 2010; Veinante and Deschenes, 2003).”

“has been implicated in an adaptive sensorimotor task requiring mice to shift flexibly between multiple auditory-motor mappings (Siniscalchi et al., 2016).”

“Therefore both feedforward and feedback pathways may compose a dynamic processing loop to detect relevant objects in space (Sreenivasan et al., 2016).”

“In addition to M1, there may be other top-down effects from frontal cortex onto S1 that may be relevant for detection and discrimination of objects ((Gilbert and Sigman, 2007; Krupa et al., 2004; van Kerkoerle et al., 2017) for”

“The results reported here were obtained with variants of either GCaMP6 (Chen et al., 2013b) or Yellow Cameleon (YC) (Horikawa et al., 2010); more recently, application of red-shifted calcium indicators also has become feasible (Bethge et al., 2017; Dana et al., 2016; Pilz et al., 2016).”

“…layers (Aronoff et al., 2010; Chen et al., 2013a) and different types of neuronal pools with distinct projection targets can be identified in vivo with the help of retrograde tracer injections and two-photon microscopy (Chen et al., 2013a; Sato and Svoboda, 2010; Yamashita et al., 2013).”

“Such information could be partially conveyed through modulation of L4 neurons, which recently have been shown to transmit touch-related thalamocortical signals while suppressing whisking signals via feedforward local inhibition (Hires et al., 2015; Gutnisky et al., 2017).”

“Furthermore, in a whisker-stimulus detection task, functional characterization of different subtypes of GABAergic interneurons revealed cell-type-specific membrane potential dynamics and spike patterns (Sachidhanandam et al., 2016; Sachidhanandam et al., 2013).”

“…a bilateral ’twoalternative forced choice’ (2AFC) discrimination task has been established, where one whisker on each side is ‘wiggled’ at variable frequencies and the rat or mouse is trained to report, on which side the higher frequency occurs (Mayrhofer et al., 2013; Musall et al., 2014) (Fig.”

“Engaging in active whisking is beneficial for the animal as it increases the likelihood of stick-slip events in a texture dependent manner (Chen et 8 al., 2015; von Heimendahl et al., 2007; Zuo et al., 2011).”

“Neural processing occurs in a spatially distributed fashion, though, and other cortical areas such as higher-order sensory areas, parietal association cortices, and frontal regions, have been implicated in stimulus representation and evaluation, too (Romo and de Lafuente, 2013; Romo et al., 2012).”

“…and discrimination thresholds (for excellent reviews see (Diamond and Arabzadeh, 2013; Romo and de Lafuente, 2013; Romo and Salinas, 2003; Stuttgen et al., 2011), we focus on experimental conditions where animals are trained to discriminate two salient stimuli that are clearly perceived…”

“whisker on each side is ‘wiggled’ at variable frequencies and the rat or mouse is trained to report, on which side the higher frequency occurs (Mayrhofer et al., 2013; Musall et al., 2014) (Fig.”

“…in specific tasks after initiating a trial with a nose poke; neural activity was often monitored by multi-unit or single-unit extracellular recordings and behavioral parameters concurrently extracted from high-speed videography (Krupa et al., 2004; Safaai et al., 2013; von Heimendahl et al., 2007).”

“Hence, typical behavioral readout parameters in these tasks are whisking angle (for individual whiskers or averaged across multiple whiskers), whisker set point, contact-induced whisker curvature change, from which lateral and axial forces impinging on the whisker follicles can be estimated (Boubenec et al., 2012; O'C…”

“Whisker-related M1 is thought to participate in whisker movement control, but its exact influence on whisker movement – whether driving, suppressive, or initiating – is still being worked out (Ebbesen et al., 2017; Sreenivasan et al., 2016).”

“19 Further progress will likely occur along multiple lines: First, head-fixed behavioral paradigms will further expand, encompassing discrimination in the auditory and visual modalities, even involving touch-screen based perception tasks (Stirman et al., 2016b), as well as higher cognitive tasks.”

“Third, new transgenic mouse lines expressing sensitive calcium indicators (Dana et al., 2014; Madisen et al., 2015) (Bethge et al., 2017) will further facilitate functional imaging of defined subsets of neurons, applied alone or in combination with viral vectors.”

“The functional role of S2 is poorly defined but may include multi-whisker processing and sensitivity to low-frequency modulation (Bokor et al., 2008; Melzer et al., 2006).”

“The functional role of S2 is poorly defined but may include multi-whisker processing and sensitivity to low-frequency modulation (Bokor et al., 2008; Melzer et al., 2006).”

“Such information could be partially conveyed through modulation of L4 neurons, which recently have been shown to transmit touch-related thalamocortical signals while suppressing whisking signals via feedforward local inhibition (Hires et al., 2015; Gutnisky et al., 2017).”

“Neural correlates of encoding of stimulus intensity and perceptual learning have been investigated for decades (Mountcastle, 1993; Romo and Salinas, 2003) and a prime role in perception has been assigned to primary sensory areas in the neocortex, which exhibit a strong relationship between…”

“One imaging study applied a special multi-area two-photon microscope, which enables simultaneous neuronal population imaging in S1 and S2 (Chen et al., 2016; Voigt et al., 2015).”

“Likewise, spike counts in barrel cortex neurons, integrated over a seconds time period, predicted well the performance of rats when they perceived pulsatile whisker stimuli (Gerdjikov et al., 2017).”

“Go/no-go (or lick/no-lick) tasks are often used in the headfixed preparation predominantly in mice and sometimes in rats (Topchiy et al., 2009; Schwarz et al., 2010; Guo et al., 2014a; Fernández et al., 2018a; Helmchen et al., 2018).”

“However, because of the strong reciprocal connections between S2 and S1, it has been difficult to identify which aspects of sensory processing are transmitted fromS2 to S1 (Helmchen et al., 2018;Minamisawa et al., 2018; Ni andChen, 2017; Petersen, 2019; Yamashita et al., 2018).”

“1) allows simultaneous imaging of many brain areas as mice perform complex behavioral tasks.(357) Sensory integration, perception, memory and learning are just several examples of the cognitive functions that can be studied using this approach.”

“Helmchen et al. (2018) reviews experiments in the so called somatosensory triangle, formed by the somatosensory primary and secondary cortex and the primary motor cortex, that contributes to sensory discrimination, and highlights the role of the primary sensory cortical layer 2/3 in vibrissae touch…”

“To test the behavioral effect of inhibiting the S1 L5 to POm projection, we used a texture discrimination task that requires S1 to S2 corticocortical communication (Chen et al., 2016; Helmchen et al., 2018; Park et al., 2022).”

“Several studies using these transgenic mice have shown correlations and causal relationships between various neural activities and behaviors under head-fixed conditions (Helmchen et al., 2018; Svoboda and Li, 2018).”

“At the cortical level, the specialized region of the barrel cortex has been extensively used to characterize the neuronal features of sensory processing related to tactile-whisker discrimination (Arabzadeh et al. 2003; Castro-Alamancos 2004; Helmchen et al. 2018).”

“Head-fixation of mice proved exceedingly useful in recent years to allow acute electrophysiological and optical recordings in awake, behaving animals (Harvey et al., 2009; Helmchen et al., 2018; Russell et al., 2022).”

“Finally, neurons involved in sensorimotor integration are expected to send information to other cortical areas to coordinate the production of movement 23,24 .”

“Headfixed mice use their whiskers [25,56] to identify differences in object texture [13], object locations [22,43], and aperture distances [35].”

“Patients with SYNGAP1 disorders are largely defined by loss-of-function SNVs leading to genetic haploinsufficiency, which leads to reduced expression of SynGAP proteins (Holder et al., 1993; Jimenez-Gomez et al., 2019; Weldon et al., 2018).”

“While 2-photon microscopy used in previous studies (10, 11, 17, 22–25) can provide access to thousands of neurons simultaneously, it is typically limited to shallow cortical layers and difficulty resolving fast neural dynamics.”

“Serial transformation of sensory inputs along the bottom-up hierarchical pathway has also been observed in rodents engaged in whisker-discrimination tasks 20,21 with an increasingly stronger association with perceptual choice in S2 22,23 and pre-motor areas 24-26 rather than whisker-related wS1 21 .”

“…(Guo et al., 2014; Laboratory et al., 2021), and several complex navigational (Glorius et al., 2024; Stuart et al., 2024), decision-making (Jung et al., 2025; Laboratory et al., 2021), sensory discrimination (Helmchen et al., 2018), and even social (Chari et al., 2023) tasks have been developed.”

“…model system, the barrel cortex circuit shares the canonical cortico-cortical architecture, including layered pyramidal neurons, defined long-range projections to motor and association areas, and feedforward and feedback pathways, that organizes sensory processing across mammalian neocortex 24,25 .”

“Along the somatosensory cortical hierarchy, categorical responses emerge in the secondary somatosensory cortex (S2) where broader receptive fields might contribute to the coding of stimulus identity or task-dependent behavioural features (Helmchen et al., 2018; Rossi-Pool et al., 2021).”

“Such paradigms include Go/No-Go tasks (Guo et al., 2014; Micallef et al., 2017; Helmchen et al., 2018), two-alternative forced-choice (2AFC) tasks (Mayrhofer et al., 2013; Guo et al., 2014; Burgess et al., 2017; Estebanez et al., 2017; Morandell and Huber, 2017; Gilad et al., 2018; Belsey et al.,…”