Inhomogeneity of visual space, discontinuity of perceptual time and cultural imprinting as exemplified with experiments on visual attention, aesthetic appreciation and temporal processing

Eines der wichtigsten Argumente für einen kognitivistischen Zugang zur Psychologie ist, dass sich die Psychologie nicht grundlegend von der Physik zu unterscheiden scheint; mentale Phänomene sind offenbar unmittelbar auf physikalische Realität bezogen. Beginnend mit der Psychophysik seit dem neunzehnten Jahrhunderts haben Experimente gezeigt, dass dieser Denkansatz nicht nur mit großen Vorteilen, sondern auch mit einigen Fallstricken verbunden sein kann. Auf der Basis des zugrundeliegenden Konzepts, dass mentale Phänomene physikalischen Ereignissen unmittelbar zugeordnet werden können, wird automatisch angenommen, dass die zeitliche Verarbeitung von sensorischen Informationen kontinuierlich sei, wie es das Zeitkonzept in der klassischen Physik nahelegt. Dieses Konzept widerspricht der Möglichkeit einer diskreten zeitlichen Informationsverarbeitung, wie sie in der Tat gilt. Des weiteren wird davon ausgegangen, dass Informationsverarbeitung in einem homogenen visuellen Wahrnehmungsraum eingebettet ist; dies ist jedoch nicht der Fall. Es wird dargestellt, dass mit einfachen sensorischen Reizen oder komplexen ästhetischen Stimuli und deren experimenteller Manipulation ein brauchbares empirisches Paradigma für ein besseres Verständnis von kognitiven Mechanismen bereitsteht, das auf diskrete zeitliche Verarbeitung und einen inhomogenen visuellen Wahrnehmungsraum hinweist. In mehreren Experimenten wird gezeigt, daß die Modulation der Aufmerksamkeit im Gesichtsfeld nicht homogen ist; Reaktionszeitexperimente mit spezifischen Modifikationen stützen die Hypothese, dass funktionell zwei Aufmerksamkeitssysteme im Gesichtsfeld eingebettet sind. Weitere unterstützende Beobachtungen über die Inhomogenität des Gesichtsfeldes kommen aus Experimenten zur ästhetischen Wahrnehmung westlicher und östlicher Kunstwerke. Diese Forschung bestätigt überdies das allgemeine Konzept von anthropologischen Universalien sowie kulturellen oder individuellen Spezifika bei der ästhetischen Wahrnehmung. Im Hinblick auf die zeitliche Wahrnehmung weisen Histogramme der Reaktionszeit auf diskrete zeitliche Informationsverarbeitung hin, was sich auch aus Beobachtungen der zeitlichen Ordnungsschwelle herleiten läßt. Bei der Untersuchung verzögerter Reaktionen wird gezeigt, dass eine präzise zeitliche Kontrolle erst nach einem längeren Intervall erreicht wird. Zusammenfassend kann man aus den verschiedenen Experimenten herleiten, dass mentale Prozesse im räumlichen und zeitlichen Bereich zwar offenkundig nicht direkt zugänglich sind, doch sollte dies nicht als eine undurchdringliche Barriere angesehen werden, um Mechanismen mentaler Prozesse zu entschlüsseln. Mit den klar definierten physikalischen Stimuli und der genauen Beachtung von Stationaritätsbedingungen bei Messungen kann diskrete zeitliche Verarbeitung und Inhomogenität des visuellen Wahrnehmungsraums gezeigt werden.One of the most compelling arguments for a cognitivist approach to psychology is that psychology does not seem to be fundamentally different from physics; mental phenomena appear to be directly related to physical reality. Experimental evidence beginning in the nineteenth century with psychophysics has shown that this approach can offer great benefits, but can suffer from some pitfalls as well. On the basis of the underlying concept that mental phenomena match directly physical events, it is automatically assumed that temporal processing of sensory information is continuous as it is assumed in classical physics neglecting the possibility of discrete temporal information processing, which in fact is the case. Furthermore, it is assumed that information processing is embedded in a homogeneous perceptual visual space; this is not the case. It is shown that the use of simple sensory stimuli or complex aesthetic stimuli and their experimental manipulation provide a useful empirical paradigm for a better understanding of the cognitive mechanisms, i.e., indicating discrete temporal processing and an inhomogeneous perceptual visual space. A number of experiments show that attentional modulation is not homogeneous in the visual field; observations using the reaction time paradigm with specific modifications support the hypothesis that two attention systems are functionally embedded in the visual field. Further supportive findings about the inhomogeneity of the visual field come from experiments on the aesthetic perception of Western and Eastern artworks. This research also confirms in addition the general concept of anthropological universals and cultural or individual specifics in aesthetic appreciation. With regard to temporal perception, reaction time distributions suggest discrete time sampling which can also be derived from observations on temporal order threshold. When testing delayed reactions after stimulus presentation, it is shown that precise temporal control is reached only after a rather long interval. It can be concluded on the basis of the different experiments that even though mental processes in the space and time domain are obviously not directly accessible, this should not be considered as an impenetrable barrier to unravel the mechanism of mental processes. Employing well-defined physical stimuli and strictly observing stationarity conditions in measurements indicate discreteness in temporal processing and inhomogeneity of visual space

The ventral basal ganglia, a selection mechanism at the crossroads of space, strategy, and reward

The basal ganglia are often conceptualised as three parallel domains that include all the constituent nuclei. The ‘ventral domain’ appears to be critical for learning flexible behaviours for exploration and foraging, as it is the recipient of converging inputs from amygdala, hippocampal formation and prefrontal cortex, putatively centres for stimulus evaluation, spatial navigation, and planning/contingency, respectively. However, compared to work on the dorsal domains, the rich potential for quantitative theories and models of the ventral domain remains largely untapped, and the purpose of this review is to provide the stimulus for this work. We systematically review the ventral domain’s structures and internal organisation, and propose a functional architecture as the basis for computational models. Using a full schematic of the structure of inputs to the ventral striatum (nucleus accumbens core and shell), we argue for the existence of many identifiable processing channels on the basis of unique combinations of afferent inputs. We then identify the potential information represented in these channels by reconciling a broad range of studies from the hippocampal, amygdala and prefrontal cortex literatures with known properties of the ventral striatum from lesion, pharmacological, and electrophysiological studies. Dopamine’s key role in learning is reviewed within the three current major computational frameworks; we also show that the shell-based basal ganglia sub-circuits are well placed to generate the phasic burst and dip responses of dopaminergic neurons. We detail dopamine’s modulation of ventral basal ganglia’s inputs by its actions on pre-synaptic terminals and post-synaptic membranes in the striatum, arguing that the complexity of these effects hint at computational roles for dopamine beyond current ideas. The ventral basal ganglia are revealed as a constellation of multiple functional systems for the learning and selection of flexible behaviours and of behavioural strategies, sharing the common operations of selection-by-disinhibition and of dopaminergic modulation

Shared action spaces:a basis function framework for social re-calibration of sensorimotor representations supporting joint action

The article explores the possibilities of formalizing and explaining the mechanisms that support spatial and social perspective alignment sustained over the duration of a social interaction. The basic proposed principle is that in social contexts the mechanisms for sensorimotor transformations and multisensory integration (learn to) incorporate information relative to the other actor(s), similar to the "re-calibration" of visual receptive fields in response to repeated tool use. This process aligns or merges the co-actors' spatial representations and creates a "Shared Action Space" (SAS) supporting key computations of social interactions and joint actions; for example, the remapping between the coordinate systems and frames of reference of the co-actors, including perspective taking, the sensorimotor transformations required for lifting jointly an object, and the predictions of the sensory effects of such joint action. The social re-calibration is proposed to be based on common basis function maps (BFMs) and could constitute an optimal solution to sensorimotor transformation and multisensory integration in joint action or more in general social interaction contexts. However, certain situations such as discrepant postural and viewpoint alignment and associated differences in perspectives between the co-actors could constrain the process quite differently. We discuss how alignment is achieved in the first place, and how it is maintained over time, providing a taxonomy of various forms and mechanisms of space alignment and overlap based, for instance, on automaticity vs. control of the transformations between the two agents. Finally, we discuss the link between low-level mechanisms for the sharing of space and high-level mechanisms for the sharing of cognitive representations

Mirror Activity in the Macaque Motor System

Mirror neurons (MirNs) within ventral premotor cortex (PMv) and primary motor cortex (M1), including pyramidal tract neurons (PTNs) projecting to the spinal cord, modulate their activity during both the execution and observation of motor acts. However, movement is not produced in the latter condition, and mirror responses cannot be explained by lowlevel muscle activity. Relatively reduced activity in M1 during observation may help to suppress movement. Here, we examined the extent to which activity at different stages of action observation reflects grasp representation and suppression of movement across multiple levels of the mirror system in monkeys and humans. We recorded MirNs in M1 and F5 (rostral PMv), including identified PTNs, in two macaque monkeys as they performed, observed, and withheld reach-to-grasp actions. Time-varying population activity was more distinct between execution and observation in M1 than in F5, and M1 activity in the lead-up to the observation of movement onset shared parallels with movement withholding activity. In separate experiments, modulation of short-latency responses evoked in hand muscles by pyramidal tract stimulation revealed modest grasp-specific facilitation at the spinal level during grasp observation. This contrasted with a relative suppression of excitability prior to observed movement onset or when monkeys simply withheld movement. Additional cortical recording experiments examined how contextual factors, such as observing to imitate, observing while engaged in action, or observation with reduced visual information, modulated mirror activity in M1 and F5. Finally, single-pulse transcranial magnetic stimulation (TMS) in healthy human volunteers was used to examine changes in corticospinal excitability (CSE) during action observation and withholding. Overall, the results reveal distinctions in the profile of mirror activity across premotor and motor areas. While F5 maintains a more abstract representation of grasp independent of the acting agent, a balance of excitation and inhibition in motor cortex and spinal circuitry during action observation may support a flexible dissociation between initiation of grasping actions and representation of observed grasp

Subcellular information processing in the olfactory system

The nervous system is tasked with the challenge of processing a variety of sensory stimuli from the environment with limited coding space and energy consumption. Recent findings challenge the traditional view of the neuron as the elementary functional unit of the nervous system, in which dendrites mainly serve as input sites, and action potential propagation through axons generates output. Instead, individual neurites have emerged as the single functional unit capable of computing inputs and generating outputs locally. Despite recent advances, the link between the mechanisms that facilitate local computations and their behavioural relevance remains unclear. I addressed this problem in Drosophila Melanogaster. The anatomical organisation of the mushroom body, a brain region associated with learning, has a compartmentalised architecture that forms the basis for local computations. My project studied subcellular signalling in the mushroom body and its role in memory formation, with emphasis on the non-spiking APL neuron that is involved in sparse odour coding and memory formation, to determine if it operates locally. To investigate this, I addressed the following points. 1. I investigated the nature of activity spread in the APL neuron. I found that input to the APL neuron evokes activity that attenuates as it propagates, supporting local computations. 2. I characterised the spatial nature of inhibition from the APL neuron onto mushroom body neurons. I found that the inhibition had a strong local effect that diminished with distance. 3. I sought to determine if there are spatial differences in the APL neuron’s response to electric shock, and if plasticity in the APL neuron is similarly spatially distinct. I found that electric shock responses are spatially distinct, but my data on plasticity was inconclusive. 4. I investigated the effects of local muscarine signalling on Kenyon cell odour responses. I found that muscarine signalling has spatially distinct effects

Aesthetic Experiences Across Cultures: Neural Correlates When Viewing Traditional Eastern or Western Landscape Paintings

Compared with traditional Western landscape paintings, Chinese traditional landscape paintings usually apply a reversed-geometric perspective and concentrate more on contextual information. Using functional magnetic resonance imaging (fMRI), we discovered an intracultural bias in the aesthetic appreciation of Western and Eastern traditional landscape paintings in European and Chinese participants. When viewing Western and Eastern landscape paintings in an fMRI scanner, participants showed stronger brain activation to artistic expressions from their own culture. Europeans showed greater activation in visual and sensory-motor brain areas, regions in the posterior cingulate cortex (PCC), and hippocampus when viewing Western compared to Eastern landscape paintings. Chinese participants exhibited greater neural activity in the medial and inferior occipital cortex and regions of the superior parietal lobule in response to Eastern compared to Western landscape paintings. On the behavioral level, the aesthetic judgments also differed between Western and Chinese participants when viewing landscape paintings from different cultures; Western participants showed for instance higher valence values when viewing Western landscapes, while Chinese participants did not show this effect when viewing Chinese landscapes. In general, our findings offer differentiated support for a cultural modulation at the behavioral level and in the neural architecture for high-level aesthetic appreciation

Exploring behavioral circuits with holographic optogenetics and network imaging

Included works This thesis contains three previously published works: Semmelhack, Donovan, et al.; eLife 2014 Temizer, Donovan, et al.; Current Biology 2015 Thiele, Donovan, Baier; Neuron 2014 And one full manuscript, soon to be in the second round of review: Dal Maschio*, Donovan*, et al. *(Equal contributions) The work presented in these manuscripts is equivalent to a standard thesis

Inimaju arvutuslikke protsesside mõistmine masinõpe mudelite tõlgendamise kaudu. Andmepõhine lähenemine arvutuslikku neuroteadusesse

Modelleerimine on inimkonna põline viis keerulistest nähtustest arusaamiseks. Planeetide liikumise mudel, gravitatsiooni mudel ja osakestefüüsika standardmudel on näited selle lähenemise edukusest. Neuroteaduses on olemas kaks viisi mudelite loomiseks: traditsiooniline hüpoteesipõhine lähenemine, mille puhul kõigepealt mudel sõnastatakse ja alles siis valideeritakse andmete peal; ja uuem andmepõhine lähenemine, mis toetub masinõpele, et sõnastada mudeleid automaatselt. Hüpoteesipõhine viis annab täieliku mõistmise sellest, kuidas mudel töötab, aga nõuab aega, kuna iga hüpotees peab olema sõnastatud ja valideeritud käsitsi. Andmepõhine lähenemine toetub ainult andmetele ja arvutuslikele ressurssidele mudelite otsimisel, aga ei seleta kuidas täpselt mudel jõuab oma tulemusteni. Me väidame, et neuroandmestike suur hulk ja nende mahu kiire kasv nõuab andmepõhise lähenemise laiemat kasutuselevõttu neuroteaduses, nihkes uurija rolli mudelite tööprintsiipide tõlgendamisele. Doktoritöö koosneb kolmest näitest neuroteaduse teadmisi avastamisest masinõppe tõlgendamismeetodeid kasutades. Esimeses uuringus tõlgendatava mudeli abiga me kirjeldame millised ajas muutuvad sageduskomponendid iseloomustavad inimese ajusignaali visuaalsete objektide tuvastamise ülesande puhul. Teises uuringus võrdleme omavahel signaale inimese aju ventraalses piirkonnas ja konvolutsiooniliste tehisnärvivõrkude aktivatsioone erinevates kihtides. Säärane võrdlus võimaldas meil kinnitada hüpoteesi, et mõlemad süsteemid kasutavad hierarhilist struktuuri. Viimane näide kasutab topoloogiat säilitavat mõõtmelisuse vähendamise ja visualiseerimise meetodit, et näha, millised ajusignaalid ja mõtteseisundid on üksteisele sarnased. Viimased tulemused masinõppes ja tehisintellektis näitasid et mõned mehhanismid meie ajus on sarnased mehhanismidega, milleni jõuavad õppimise käigus masinõppe algoritmid. Oma tööga me rõhutame masinõppe mudelite tõlgendamise tähtsust selliste mehhanismide avastamiseks.Building a model of a complex phenomenon is an ancient way of gaining knowledge and understanding of the reality around us. Models of planetary motion, gravity, particle physics are examples of this approach. In neuroscience, there are two ways of coming up with explanations of reality: a traditional hypothesis-driven approach, where a model is first formulated and then tested using the data, and a more recent data-driven approach, that relies on machine learning to generate models automatically. Hypothesis-driven approach provides full understanding of the model, but is time-consuming as each model has to be conceived and tested manually. Data-driven approach requires only the data and computational resources to sift through potential models, saving time, but leaving the resulting model itself to be a black box. Given the growing amount of neural data, we argue in favor of a more widespread adoption of the data-driven approach, reallocating part of the human effort from manual modeling. The thesis is based on three examples of how interpretation of machine-learned models leads to neuroscientific insights on three different levels of neural organization. Our first interpretable model is used to characterize neural dynamics of localized neural activity during the task of visual perceptual categorization. Next, we compare the activity of human visual system with the activity of a convolutional neural network, revealing explanations about the functional organization of human visual cortex. Lastly, we use dimensionality reduction and visualization techniques to understand relative organization of mental concepts within a subject's mental state space and apply it in the context of brain-computer interfaces. Recent results in neuroscience and AI show similarities between the mechanisms of both systems. This fact endorses the relevance of our approach: interpreting the mechanisms employed by machine learning models can shed light on the mechanisms employed by our brainhttps://www.ester.ee/record=b536057

Computational techniques to interpret the neural code underlying complex cognitive processes

Advances in large-scale neural recording technology have significantly improved the capacity to further elucidate the neural code underlying complex cognitive processes. This thesis aimed to investigate two research questions in rodent models. First, what is the role of the hippocampus in memory and specifically what is the underlying neural code that contributes to spatial memory and navigational decision-making. Second, how is social cognition represented in the medial prefrontal cortex at the level of individual neurons. To start, the thesis begins by investigating memory and social cognition in the context of healthy and diseased states that use non-invasive methods (i.e. fMRI and animal behavioural studies). The main body of the thesis then shifts to developing our fundamental understanding of the neural mechanisms underpinning these cognitive processes by applying computational techniques to ana lyse stable large-scale neural recordings. To achieve this, tailored calcium imaging and behaviour preprocessing computational pipelines were developed and optimised for use in social interaction and spatial navigation experimental analysis. In parallel, a review was conducted on methods for multivariate/neural population analysis. A comparison of multiple neural manifold learning (NML) algorithms identified that non linear algorithms such as UMAP are more adaptable across datasets of varying noise and behavioural complexity. Furthermore, the review visualises how NML can be applied to disease states in the brain and introduces the secondary analyses that can be used to enhance or characterise a neural manifold. Lastly, the preprocessing and analytical pipelines were combined to investigate the neural mechanisms in volved in social cognition and spatial memory. The social cognition study explored how neural firing in the medial Prefrontal cortex changed as a function of the social dominance paradigm, the "Tube Test". The univariate analysis identified an ensemble of behavioural-tuned neurons that fire preferentially during specific behaviours such as "pushing" or "retreating" for the animal’s own behaviour and/or the competitor’s behaviour. Furthermore, in dominant animals, the neural population exhibited greater average firing than that of subordinate animals. Next, to investigate spatial memory, a spatial recency task was used, where rats learnt to navigate towards one of three reward locations and then recall the rewarded location of the session. During the task, over 1000 neurons were recorded from the hippocampal CA1 region for five rats over multiple sessions. Multivariate analysis revealed that the sequence of neurons encoding an animal’s spatial position leading up to a rewarded location was also active in the decision period before the animal navigates to the rewarded location. The result posits that prospective replay of neural sequences in the hippocampal CA1 region could provide a mechanism by which decision-making is supported

Neuronal representation of sound source location in the auditory cortex during active navigation

The ability to localize sounds is crucial for the survival of both predators as well as prey. The former rely on their senses to lead them to the latter, which in turn also benefit from locating a predator in the vicinity to escape accordingly. In such cases, the sound localization process typically takes place while the animals are in motion. Since the cues that the brain uses to localize sounds are head-centered (egocentric), they can change very rapidly when an animal moves and rotates. This constitutes an even bigger challenge than sound localization in a static environment. Up to now, however, both aspects have mostly been studied separately in neuroscience, thus limiting our understanding of active sound localization during navigation. This thesis reports on the development of a novel behavioral paradigm – the Sensory Island Task (SIT) – to promote sound localization during unrestricted motion. By attributing a different behavioral meaning (associated to different outcomes) to two spatially separated sound sources, Mongolian gerbils (Meriones unguiculatus) were trained to forage for an area (target island) in the arena that triggered a change in the active sound source to the target loudspeaker and to report its detection by remaining within the island for a duration of 6 s. Importantly, the two loudspeakers played identical sounds and the location of the target island in the arena was changed randomly every trial. When the probability of successfully identifying the target island exceeded the chance level, a tetrode bundle was implanted in the primary auditory cortex of the gerbils to record neuronal responses during task performance. Canonically, the auditory cortex (AC) is described as possessing neurons with a broad hemispheric tuning. Nonetheless, context and behavioral state have been shown to modulate the neuronal responses in the AC. The experiments described in this thesis demonstrate the existence of a large variety of additional, previously unreported (or underreported) spatial tuning types. In particular, neurons that were sensitive to the midline and, most intriguingly, neurons that were sensitive to the task identity of the active loudspeaker were observed. The latter comprise neurons that were spatially tuned to only one of the two loudspeakers, neurons that exhibited a large difference in the preferred egocentric sound-source location for the two loudspeakers as well as spatially untuned neurons whose firing rate changed depending on the active loudspeaker. Additionally, temporal complexity in the neuronal responses was observed, with neurons changing their preferred egocentric sound-source location throughout their response to a sound. Corroborating earlier studies, also here it was found that the task-specific choice of the animal was reflected in the neuronal responses. Specifically, the neuronal firing rate decreased before the animal successfully finished a trial in comparison to situations in which the gerbil incorrectly left the target island before trial completion. Furthermore, the differential behavioral meaning between the two loudspeakers was found to be represented in the neuronal tuning acuity, with neurons being more sharply tuned to sounds coming from the target than from the background loudspeaker. Lastly, by implementing an artificial neural network, all of the observed phenomena could be studied in a common framework, enabling a better and more comprehensive understanding of the computational relevance of the diversity of observed neuronal responses. Strikingly, the algorithm was capable of predicting not only the egocentric sound-source location but also which sound source was active – both with high accuracy. Taken together, the results presented in this thesis suggest the existence of an interlaced coding of egocentric and allocentric information in the neurons of the primary auditory cortex. These novel findings thus contribute towards a better understanding of how sound sources are perceptually stable during self-motion, an effect that could be advantageous for selective hearing