Acquisition Of Sensory Information Research Articles

Rapid assessment of hand reaching using virtual reality and application in cerebellar stroke.

The acquisition of sensory information about the world is a dynamic and interactive experience, yet the majority of sensory research focuses on perception without action and is conducted with participants who are passive observers with very limited control over their environment. This approach allows for highly controlled, repeatable experiments and has led to major advances in our understanding of basic sensory processing. Typical human perceptual experiences, however, are far more complex than conventional action-perception experiments and often involve bi-directional interactions between perception and action. Innovations in virtual reality (VR) technology offer an approach to close this notable disconnect between perceptual experiences and experiments. VR experiments can be conducted with a high level of empirical control while also allowing for movement and agency as well as controlled naturalistic environments. New VR technology also permits tracking of fine hand movements, allowing for seamless empirical integration of perception and action. Here, we used VR to assess how multisensory information and cognitive demands affect hand movements while reaching for virtual targets. First, we manipulated the visibility of the reaching hand to uncouple vision and proprioception in a task measuring accuracy while reaching toward a virtual target (n = 20, healthy young adults). The results, which as expected revealed multisensory facilitation, provided a rapid and a highly sensitive measure of isolated proprioceptive accuracy. In the second experiment, we presented the virtual target only briefly and showed that VR can be used as an efficient and robust measurement of spatial memory (n = 18, healthy young adults). Finally, to assess the feasibility of using VR to study perception and action in populations with physical disabilities, we showed that the results from the visual-proprioceptive task generalize to two patients with recent cerebellar stroke. Overall, we show that VR coupled with hand-tracking offers an efficient and adaptable way to study human perception and action.

The effect of normoxia exposure on hypoxia tolerance and sensory sampling in a swamp-dwelling mormyrid fish

Effects of energetic limitations on the performance of sensory systems are generally difficult to quantify. Weakly electric fishes provide an ideal model system to quantify the effects of metabolic stressors on sensory information acquisition, because they use an active-sensing strategy that permits easy measurement of the sensing effort. These fishes discharge an electric signal and sense perturbations of the resulting electric field. We used the mormyrid Petrocephalus degeni to quantify the relationship between routine metabolic rate and the rate of sensory sampling (rate of electric organ discharge, EOD) while under progressive hypoxia by quantifying the critical oxygen tension (PC-MR) and the critical electric organ discharge threshold (PC-EOD). PC-MR was significantly higher in fish acclimated to normoxia for over 40 days compared to animals tested within 1-5 days of capture from a hypoxic swamp, which suggests high costs of maintaining hypoxia tolerance; however, there was no acclimation effect on PC-EOD. All P. degeni reached their PC-EOD prior to their PC-MR. However, below the respective critical tension value, EOD rate decreased more gradually than the metabolic rate suggesting that the fish were increasing the proportion of their energy budget allocated to acquiring sensory information as dissolved-oxygen levels dropped. Trade-offs between sensory sampling and other physiological functions are also suggested by the increase in routine EOD rate with long-term normoxia acclimation, in contrast to metabolic rate, which showed no significant changes. These results highlight the relationship between sensory sampling and metabolic rate in response to progressive hypoxia and the plasticity of hypoxia tolerance.

Local Sleep Oscillations: Implications for Memory Consolidation.

Accumulating evidence suggests that sleep is important for plasticity and memory consolidation (Maquet, 2001; Walker and Stickgold, 2004; Datta and Maclean, 2007; Diekelmann and Born, 2010; Tononi and Cirelli, 2014; Dudai et al., 2015)—the transformation of new labile memories encoded in wakefulness into stable representations that integrate into long-term memory networks. A central model accounting for memory consolidation during sleep is that of coupling between hippocampal (HC) and neocortical networks (Buzsaki, 1996). According to this two-stage model of memory formation [also termed the hippocampal—neocortical dialogue model (Buzsaki, 1989)], the dominant direction of information flow across the brain differs between wake and sleep periods. During wakefulness, acquisition of sensory information mainly drives signal propagation from cortex to hippocampus (HC) (Buzsaki, 1998; Mormann et al., 2008). By contrast, during subsequent non-rapid eye movement (NREM) sleep, this model suggests a central role for information flow from HC to cortex especially around sharp-wave ripples (SWRs) events (Buzsaki, 1998). Accordingly, slow waves that originate in the neocortex repeatedly reactivate the newly encoded HC information when SWRs occur, driving subsequent activity in select cortical circuits (Siapas and Wilson, 1998). However, it is clear that information flow is not strictly unidirectional (Wagner et al., 2010) and may involve complex loops (Rothschild et al., 2017). HC reactivation tends to co-occur with sleep spindles that optimize plasticity (Seibt et al., 2017), resulting in long-term modification of synaptic efficacy. Thus, hippocampal–neocortical coupling requires interregional cross-frequency coordination between sleep oscillations, including slow waves and sleep spindles in thalamo-cortical circuits as well as HC ripples. The underlying prevalent assumption is that sleep oscillations (slow waves in particular) are global events that co-occur nearly simultaneously across different brain regions. But in fact, they have been described as traveling waves propagating from anterior-to-posterior cortex (Massimini et al., 2004), and they typically occur out of phase across different cortical sites (Nir et al., 2011; Vyazovskiy et al., 2011; Malerba et al., 2019). How can we reconcile models requiring co-occurrence of sleep oscillations with accumulating evidence of non-uniform timing of oscillations across the brain? In this article, we first review the current data that sheds light on this question, and highlight recent studies that link regional coupling of sleep oscillations with consolidation of specific memories. Then, we highlight the gap between sleep and memory theory and experimental evidence. Based on studies that monitor and manipulate specific cortical circuits, we propose that coupling can occur between sleep oscillations in general, and between HC and cortex specifically, but that such coupling likely involves different brain regions at each point in time, contributing to memory consolidation in select circuits.

Effects of hypoxia on swimming and sensing in a weakly electric fish.

Low dissolved oxygen (hypoxia) can severely limit fish performance, especially aerobically expensive behaviours including swimming and acquisition of sensory information. Fishes can reduce oxygen requirements by altering these behaviours under hypoxia, but the underlying mechanisms can be difficult to quantify. We used a weakly electric fish as a model system to explore potential effects of hypoxia on swim performance and sensory information acquisition, which enabled us to non-invasively record electric signalling activity used for active acquisition of sensory information during swimming. To quantify potential effects of hypoxia, we measured critical swim speed (Ucrit) and concurrent electric signalling activity under high- and low-dissolved oxygen concentrations in a hypoxia-tolerant African mormyrid fish, Marcusenius victoriae Fish were maintained under normoxia for 6 months prior to experimental treatments, and then acclimated for 8 weeks to normoxia or hypoxia and tested under both conditions (acute: 4 h exposure). Acute hypoxia exposure resulted in a significant reduction in both Ucrit and electric signalling activity in fish not acclimated to hypoxia. However, individuals acclimated to chronic hypoxia were characterized by a higher Ucrit under both hypoxia and normoxia than fish acclimated to normoxia. Following a 6 month re-introduction to normoxia, hypoxia-acclimated individuals still showed increased performance under acute hypoxic test conditions, but not under normoxia. Our results highlight the detrimental effects of hypoxia on aerobic swim performance and sensory information acquisition, and the ability of fish to heighten aerobic performance through acclimation processes that can still influence performance even months after initial exposure.

Task-specific sensory coding strategies are matched to detection and discrimination performance.

The acquisition of sensory information is limited by the neural encoding method used, constraining perceptual abilities. The most relevant aspects of stimuli may change as behavioral context changes, making efficient encoding of information more challenging. Sensory systems must balance rapid detection of a stimulus with perception of fine details that enable discrimination between similar stimuli. Here, we show that in a species of weakly electric fish, Apteronotus leptorhynchus, two coding strategies are employed for these separate behavioral tasks. Using communication signals, we demonstrate a strong correlation between neural coding strategies and behavioral performance on a discrimination task. Extracellular recordings of pyramidal cells within the electrosensory lateral line lobe of alert fish show two distinct response patterns, either burst discharges with little variation between different signals of the same category, or a graded, heterogeneous response that contains sufficient information to discriminate between signals with slight variations. When faced with a discrimination-based task, the behavioral performance of the fish closely matches predictions based on coding strategy. Comparisons of these results with neural and behavioral responses observed in other model systems suggest that our study highlights a general principle in the way sensory systems utilize different neural codes.

Hypoxia acclimation increases novelty response strength during fast-starts in the African mormyrid, Marcusenius victoriae

Many fishes perform quick and sudden swimming maneuvers known as fast-starts to escape when threatened. In pulse-type weakly electric fishes these responses are accompanied by transient increases in the rate of electric signal production known as novelty responses. While novelty responses may increase an individual's information about their surroundings, they are aerobically powered and may come at a high energetic cost when compared to fast-starts, which rely primarily on anaerobic muscle. The juxtaposition between two key aspects of fast-starts in these fishes - the aerobic novelty response and the anaerobic swimming performance - makes them an interesting model for studying effects of hypoxia on escape performance and sensory information acquisition. We acclimated the hypoxia-tolerant African mormyrid Marcusenius victoriae to either high or low dissolved oxygen (DO) levels for 8weeks, after which fast-starts and novelty responses were quantified under both high (normoxic) and low-DO (hypoxic) test conditions. Hypoxia-acclimated fish exhibited higher maximum curvature than normoxia-acclimated fish. Displacement of normoxia-acclimated fish was not reduced under acute hypoxic test conditions. Novelty responses were given upon each startle, whether or not the fish performed a fast-start; however, novelty responses associated with fast-starts were significantly stronger than those without, suggesting a functional link between fast-start initiation and the motor control of the novelty response. Overall, hypoxia-acclimated individuals produced significantly stronger novelty responses during fast-starts. We suggest that increased novelty response strength in hypoxia-acclimated fish corresponds to an increased rate of sensory sampling, which may compensate for potential negative effects of hypoxia on higher-level processing.

Sensory Flow as a Basis for a Novel Distance Cue in Freely Behaving Electric Fish

The sensory input that an animal receives is directly linked to its motor activity. Behavior thus enables animals to influence their sensory input, a concept referred to as active sensing. How such behavior can serve as a scaffold for generating sensory information is of general scientific interest. In this article, we investigate how behavior can shape sensory information by using some unique features of the sensorimotor system of the weakly electric fish. Based on quantitative behavioral characterizations and computational reconstruction of sensory input, we show how electrosensory flow is actively created during highly patterned, spontaneous behavior in Gnathonemus petersii. The spatiotemporal structure of the sensory input provides information for the computation of a novel distance cue, which allows for a continuous estimation of distance. This has significant advantages over previously known nondynamic distance estimators as determined from electric image blur. Our investigation of the sensorimotor interactions in pulsatile electrolocation shows, for the first time, that the electrosensory flow contains behaviorally relevant information accessible only through active behavior. As patterned sensory behaviors are a shared feature of (active) sensory systems, our results have general implications for the understanding of (active) sensing, with the proposed sensory flow-based measure being potentially pertinent to a broad range of sensory modalities. <b>SIGNIFICANCE STATEMENT</b> Acquisition of sensory information depends on motion, as either an animal or its sensors move. Behavior can thus actively influence the sensory flow; and in this way, behavior can be seen as a manifestation of the brain9s integrative functions. The properties of the active pulsatile electrolocation system in Gnathonemus petersii allow for the sensory input to be computationally reconstructed, enabling us to link the informational content of spatiotemporal sensory dynamics to behavior. Our study reveals a novel sensory cue for estimating depth that is actively generated by the fishes9 behavior. The physical and behavioral similarities between electrolocation and other active sensory systems suggest that this may be a mechanism shared by (active) sensory systems.

Simulation of feedback-driven PCR assays on a 2D electrowetting array using a domain-specific high-level biological programming language

The motivation of our work is to demonstrate that scientists can describe biochemical assays using a high-level domain-specific programming language and can execute them automatically on a two-dimensional electrowetting array featuring integrated sensors that provide feedback in real-time to the host PC that controls the integrated system. The fundamental research problem that this paper addresses is how to express, at a high level of abstraction, the acquisition of sensory information from the device, and the computation on that data, which is required to perform real-time decision making in response. The approach that we have taken is first, to create a new version of BioCoder, a programming language for automated biology, which we have specialized for electrowetting arrays featuring integrated sensors, and second, to use this language to specify two feedback-driven Polymerase Chain Reaction (PCR) assays at the desired level of abstraction. Our methodology is to evaluate the performance of these assays using a custom-build runtime system to control the execution of feedback-driven assays on a cycle-accurate software simulator that accurately characterizes the behavior of the electrowetting platform during assay execution. The result of this experiment is successful simulation of these non-trivial feedback-driven assays, starting from a high-level specification, which allows us to conclude that high-level programming language design and implementation targeting electrowetting (or other competing laboratory-on-a-chip technologies) is feasible. • Biochemical reactions described using a high-level programming language • Reactions compiled onto a “digital microfluidic” electrowetting chip • Control software performs real-time decision-making based on sensory feedback. • Software simulation of execution of two feedback-driven PCR assays

Chemosensory Perception of Predators by Larval Amphibians Depends on Water Quality.

The acquisition of sensory information by animals is central to species interactions. In aquatic environments, most taxa use chemical cues to assess predation risk and other key ecological factors. A number of laboratory studies suggest that anthropogenic pollutants can disrupt chemoreception, even when at low, non-toxic concentrations, but there are few tests of whether real-world variation in water quality affects chemoreception. Here we investigate whether chemosensory perception of predators by the gray treefrog, Hyla versicolor, depends on water quality. We evaluated the anti-predator response of anuran tadpoles housed in water collected from three sites that represent strong contrasts in the concentration and types of dissolved solids: de-chlorinated tap water, water from an impaired stream, and treated wastewater effluent. Behavioral assays were conducted in laboratory aquaria. Chemical cues associated with predation were generated by feeding tadpoles to dragonfly predators held in containers, and then transferring aliquots of water from dragonfly containers to experimental aquaria. Tadpoles housed in tap water responded to predator cues with an activity reduction of 49%. Tadpoles housed in stream water and wastewater effluent responded to predator cues by reducing activity by 29% and 24% respectively. The results of factorial ANOVA support the hypothesis that the response to predator cues depended on water type. These results show that alteration of the chemical environment can mediate chemical perception of predators in aquatic ecosystems. Because most aquatic species rely on chemoreception to gather information on the location of food and predators, any impairment of sensory perception likely has important ecological consequences.

From Perception to Action: A Spatiotemporal Cortical Map

In this issue of Neuron, Guo etal. (2014) optogenetically probe contributions of different cortical regions totactile sensory perception, finding that somatosensory cortex is necessary for acquisition of sensory information and frontal cortex is necessary for planning motor output.

Sensory flow shaped by active sensing: sensorimotor strategies in electric fish

Goal-directed behavior in most cases is composed of a sequential order of elementary motor patterns shaped by sensorimotor contingencies. The sensory information acquired thus is structured in both space and time. Here we review the role of motion during the generation of sensory flow focusing on how animals actively shape information by behavioral strategies. We use the well-studied examples of vision in insects and echolocation in bats to describe commonalities of sensory-related behavioral strategies across sensory systems, and evaluate what is currently known about comparable active sensing strategies in electroreception of electric fish. In this sensory system the sensors are dispersed across the animal's body and the carrier source emitting energy used for sensing, the electric organ, is moved while the animal moves. Thus ego-motions strongly influence sensory dynamics. We present, for the first time, data of electric flow during natural probing behavior in Gnathonemus petersii (Mormyridae), which provide evidence for this influence. These data reveal a complex interdependency between the physical input to the receptors and the animal's movements, posture and objects in its environment. Although research on spatiotemporal dynamics in electrolocation is still in its infancy, the emerging field of dynamical sensory systems analysis in electric fish is a promising approach to the study of the link between movement and acquisition of sensory information.

SEEING AND COMMUNICATING THROUGH WEAK ELECTRIC FIELDS

![][1] Weakly electric fish spend their lives bathed in their own internally generated mild electric field, interpreting perturbations in the field as objects pass through and when communicating with members of their own species through high frequency electric ‘chirps’. Rudiger

Testing the Sorption Hypothesis in Olfaction: A Limited Role for Sniff Strength in Shaping Primary Odor Representations During Behavior

The acquisition of sensory information during behavior shapes the neural representation, central processing, and perception of external stimuli. In mammals, a sniff represents the basic unit of odor sampling, yet how sniffing shapes odor representations remains poorly understood. Perhaps the earliest hypothesis of the role of sniffing in olfaction arises from the fact that odorants with different physicochemical properties exhibit different patterns of deposition across the olfactory epithelium, and that these patterns are differentially affected by flow rate. However, whether sniff flow rates shape odor representations during natural sniffing remains untested, and whether animals make use of odorant sorption-airflow relationships as part of an active odor-sampling strategy remains unclear. We tested these ideas in the intact rat using a threefold approach. First, we asked whether sniff strength shapes odor representations in vivo by imaging from olfactory receptor neuron (ORN) terminals during controlled changes in inhalation flow in the anesthetized rat. Second, we asked whether sniff strength shapes odor representations by imaging from ORNs during natural sniffing in the awake rat. Third, we asked whether rats actively modulate sniff strength during an odor discrimination task. We found that, while artificial changes in flow rate can alter ORN responses, sniff strength has negligible effect on odor representations during natural sniffing, and behaving rats do not modulate flow rate to improve odor discrimination. These data suggest that modulating sniff strength does not shape odor representations sufficiently to be part of a strategy for active odor sensing in the behaving animal.

Blinded by the stink: Nutrient enrichment impairs the perception of predation risk by freshwater snails

The acquisition of sensory information is central to all species interactions. Most aquatic organisms use chemical cues to assess predation risk and other key ecological factors, but chemoreception may be disrupted in systems with elevated pH. Elevated pH in lakes and rivers is often associated with eutrophication. We used laboratory and mesocosm experiments to test whether elevated pH impairs perception of predation risk by the freshwater snails Physa acuta and Helisoma trivolvis. In one set of experiments, nutrients were added to outdoor mesocosms, resulting in mid-afternoon pH values of 8.5-9.7. Both snail species moved to avoid fish in water with pH < 9.0 but showed no avoidance at higher pH. In a laboratory study, we used buffers to establish six pH treatments ranging from 7.5 to 10.0. At lower pH Physa acuta responded to fish cues by moving into safer habitats, but avoidance became impaired at a pH of 9.4. Helisoma trivolvis also responded to fish at lower pH, and their avoidance behavior became impaired at a pH of 8.8. Given the diversity of aquatic organisms that depend on reception of chemical cues and the broad extent of eutrophication, chemosensory impairment is likely a common occurrence in nature.

Isolated elevated aldolase as a marker for a myositis subtype: another branch to the polymyositis tree

The sensory input that an animal receives is directly linked to its motor activity. Behavior thus enables animals to influence their sensory input, a concept referred to as active sensing....

Error reduction during visual processing by the retina—a paradigm for sensor design

We use a general second-order mathematical description of sensing, sensory information acquisition and pre-processing to treat biological vision in analogy to a technical sensor. Using very early visual processing by the retina, i.e. the retinal receptive fields, we compare the structure of interconnection of photoreceptors, bipolar and ganglion cells that evolved in vertebrates with other structures of interconnections that would serve the same purpose of generating an image of contrasts and supplying it to the brain. We are able to show that the ladder-type structure of the vertebrate retina approaches ideal behaviour (with respect to high linearity and low error sensitivity) and is the structure most tolerant to imperfection of its constituent elements, the different nerve cells. Since the model presented is very general, it can be applied to other sensory systems as well. The application of the sensory structure of the retina (which, from the biological modelling point of view, derives in a straightforward way from known facts about retina physiology) is useful if applied to sensor design. In particular it shows how nonlinearities, error- and cross sensitivities of the entire sensor system can be reduced by the structure among its elements.

Involvement of GABAergic and cholinergic medial septal neurons in hippocampal theta rhythm

Hippocampal theta rhythm (HPCtheta) may be important for various phenomena, including attention and acquisition of sensory information. Two types of HPCtheta (types I and II) exist based on pharmacological, behavioral, and electrophysiological characteristics. Both types occur during locomotion, whereas only type II (atropine-sensitive) is present under urethane anesthesia. The circuit of HPCtheta synchronization includes the medial septum-diagonal band of Broca (MSDB), with cholinergic and gamma-aminobutyric acid (GABA)ergic neurons comprising the two main projections from MSDB to HPC. The primary aim of the present study was to assess the effects of GABAergic MSDB lesions on urethane- and locomotion-related HPCtheta, and compare these effects to those of cholinergic MSDB lesions. Saline, kainic acid (KA), or 192 IgG-saporin (SAP) was injected into MSDB before recording. KA preferentially destroys GABAergic MSDB neurons, whereas SAP selectively eliminates cholinergic MSDB neurons. A fixed recording electrode was placed in the dentate mid-molecular layer, and stimulating electrodes were placed in the posterior hypothalamus (PH), and medial perforant path (PP). Under urethane anesthesia, HPCtheta was induced by tail pinch, PH stimulation, and systemic physostigmine; none of the rats with KA or SAP showed HPCtheta in any of these conditions. During locomotion, HPCtheta was attenuated, but not eliminated, in rats with KA or SAP lesions. Intraseptal KA in combination with either intraseptal SAP or PP lesions reduced locomotion-related HPCtheta beyond that observed with each lesion alone, virtually eliminating HPCtheta. In contrast, intraseptal SAP combined with PP lesions did not reduce HPCtheta beyond the effect of each lesion alone. We conclude that both GABAergic and cholinergic MSDB neurons are necessary for HPCtheta under urethane, and that each of these septohippocampal projections contributes to HPCtheta during locomotion.

Collision-free Motion Planning for a Cucumber Picking Robot

Abstract One of the most challenging aspects of the development, at the Institute of Agricultural and Environmental Engineering (IMAG B.V.), of an automatic harvesting machine for cucumbers was to achieve a fast and accurate eye–hand co-ordination during the picking operation. This paper presents a procedure developed for the cucumber harvesting robot to pursue this objective. The procedure contains two main components. First of all acquisition of sensory information about the working environment of the robot and, secondly, a program to generate collision-free manipulator motions to direct the end-effector to and from the cucumber. This paper elaborates on the latter. Collision-free manipulator motions were generated with a so-called path search algorithm. In this research the A*-search algorithm was used. With some numerical examples the search procedure is illustrated and analysed in view of application to cucumber harvesting. It is concluded that collision-free motions can be calculated for the seven degrees-of-freedom manipulator used in the cucumber picking device. The A*-search algorithm is easy to implement and robust. This algorithm either produces a solution or stops when a solution cannot be found. This favourable property, however, makes the algorithm prohibitively slow. The results showed that the algorithm does not include much intelligence in the search procedure. It is concluded that to meet the required 10 s for a single harvest cycle, further research is needed to find fast algorithms that produce solutions using as much information about the particular structure of the problem as possible and give a clear message if such a solution can not be found.

Tactile Responses in the Granule Cell Layer of Cerebellar Folium Crus IIa of Freely Behaving Rats

We recorded activity from the granule cell layer (GCL) of cerebellar folium Crus IIa as freely moving rats engaged in a variety of natural behaviors, including grooming, eating, and free tactile exploration. Multiunit responses in the 1000-4500 Hz range were found to be strongly correlated with tactile stimulation of lip and whisker (perioral) regions. These responses occurred regardless of whether the stimulus was externally or self-generated and during both active and passive touch. In contrast, perioral movements that did not tactually stimulate this region of the face (e.g., chewing) produced no detectable increases in GCL activity. In addition, GCL responses were not correlated with movement extremes. When rats used their lips actively for palpation and exploration, the tactile responses in the GCL were not detectably modulated by ongoing jaw movements. However, active palpation and exploratory behaviors did result in the largest and most continuous bursts of GCL activity: responses were on average 10% larger and 50% longer during palpation and exploration than during grooming or passive stimulation. Although activity levels differed between behaviors, the position and spatial extent of the peripheral receptive field was similar over all behaviors that resulted in tactile input. Overall, our data suggest that the 1000-4500 Hz multiunit responses in the Crus IIa GCL of awake rats are correlated with tactile input rather than with movement or any movement parameter and that these responses are likely to be of particular importance during the acquisition of sensory information by perioral structures.

Modulation of Forebrain Electroencephalographic Activity and Behavioral State by the Locus Ceruleus-Noradrenergic System: Involvement of the Medial Septal Area

This chapter summarizes a series of studies in the halothane-anesthetized rat to directly assess the causal relationship between locus coeruleus (LC) neuronal discharge activity and forebrain electroencephalographic activity (EEG) state. The chapter demonstrates substantial tonic excitatory actions of the LC noradrenergic system on electroencephalographic activity. The results indicate that the LC-noradrenergic system is a potent modulator of forebrain EEG state via actions of β receptors in the halothane-anesthetized rat. Under these experimental conditions, noradrenergic efferents, presumably arising from LC, modulate forebrain EEG state via actions at MS β receptors. However, to obtain a clearer understanding of the behavioral functions of the LC-noradrenergic system additional studies have been conducted. Based on these observations and those of others, it is posited that one function of LC is to facilitate the induction of a behavioral state appropriate for acquisition of sensory information. This is proposed to be dependent on changes in the tonic activity of LC neurons associated with changes in behavioral state and, at least in part, involves actions of norepinephrine (NE) at β receptors located within the MS. Superimposed on these actions may be facilitatory actions on state-dependent cognitive processes that may, in part, involve phasic fluctuations in LC neuronal activity and possibly actions of NE within cortical and thalamic terminal fields. Combined, these actions would serve to facilitate appropriate behavioral responding to sensory information.