Spreadsheet analysis of a hierarchical control system model of behavior

The behavior of a hierarchy of control systems can be simulated with an electronic-spreadsheet. Each control system is a column of three cells representing the reference signal, perceptual signal, and output variable of the system. All of the control systems are closed-loop, the input to each system being a function of its output. The circular references in the spreadsheet are resolved through iterative recalculation. When the parameters of each control system (amplification and slowing factors) are set to appropriate values, all control systems in the hierarchy continue to match perceptual signals with reference signals. A three-level hierarchy with four systems at each level is simulated in the spreadsheet. The spreadsheet model makes it possible to observe the dynamic behavior of the control systems as they correct for the effects of environmental disturbance and changes in higher order reference signals. It is possible to “reorganize” the system by changing the perceptions controlled by systems at different levels of the hierarchy. The user can also test to determine the variables being controlled by the system.     

A low-cost spatial contrast sensitivity display driver

The circuit described here can provide the line and frame signals to drive anx, y display scope or oscilloscope at high resolution (1,000 lines) and repetition rate (50 Hz). Synchronizing circuitry at the input of the circuit allows the raster scan to be locked to an input signal, such as the square-wave output from a function generator, while another waveform from the same function genera-tor, the sine output, drives the z (intensity) input of the display scope. A stable spatial contrast display results. Spatial contrast depth is a direct function of z input modulation voltage. Spatial frequency is a direct function of the function generator frequency. The circuit can be used with a programmable function generator under computer control.     

The Organization of Extrinsic Neurons and Their Implications in the Functional Roles of the Mushroom Bodies in Drosophila melanogaster Meigen

Although the importance of the Drosophila mushroom body in olfactory learning and memory has been stressed, virtually nothing is known about the brain regions to which it is connected. Using Golgi and GAL4–UAS techniques, we performed the first systematic attempt to reveal the anatomy of its extrinsic neurons. A novel presynaptic reporter construct, UAS-neuronal synaptobrevin–green fluorescent protein (n-syb–GFP), was used to reveal the direction of information in the GAL4-labeled neurons. Our results showed that the main target of the output neurons from the mushroom body lobes is the anterior part of the inferior medial, superior medial, and superior lateral protocerebrum. The lobes also receive afferents from these neuropils. The lack of major output projections directly to the deutocerebrum’s premotor pathways discourages the view that the role of the mushroom body may be that of an immediate modifier of behavior. Our data, as well as a critical evaluation of the literature, suggest that the mushroom body may not by itself be a “center” for learning and memory, but that it can equally be considered as a preprocessor of olfactory signals en route to “higher” protocerebral regions.     

Multiple parallel memory systems in the brain of the rat

A theory of multiple parallel memory systems in the brain of the rat is described. Each system consists of a series of interconnected neural structures. The "central structures" of the three systems described are the hippocampus, the matrix compartment of the dorsal striatum (caudate-putamen), and the amygdala. Information, coded as neural signals, flows independently through each system. All systems have access to the same information from situations in which learning occurs, but each system is specialized to represent a different kind of relationship among the elements (stimulus events, responses, reinforcers) of the information that flows through it. The speed and accuracy with which a system forms a coherent representation of a learning situation depend on the correspondence between the specialization of the system and the relationship among the elements of the situation. The coherence of these stored representations determines the degree of control exerted by each system on behavior in the situation. Although they process information independently the systems interact in at least two ways: by simultaneous parallel influence on behavioral output and by directly influencing each other. These interactions can be cooperative (leading to similar behaviors) or competitive (leading to different behaviors). Experimental findings consistent with these ideas, mostly from experiments with rats, are reviewed.     

Consistency of vertebral motion and individual characteristics in gait sequences

Vertebral motion reveals complex patterns, which are not yet understood in detail. This applies to vertebral kinematics in general but also to specific motion tasks like gait. For gait analysis, most of existing publications focus on averaging characteristics of recorded motion signals. Instead, this paper aims at analyzing intra- and inter-individual variation specifically and elaborating motion parameters, which are consistent during gait cycles of particular persons. For this purpose, a study design was utilized, which collected motion data from 11 asymptomatic test persons walking at different speed levels (2, 3, and 4 km/h). Acquisition of data was performed using surface topography. The motion signals were preprocessed in order to separate average vertebral orientations (neutral profiles) from basic gait cycles. Subsequently, a k-means clustering technique was applied to figure out, whether a discrimination of test persons was possible based on the preprocessed motion signals. The paper shows that each test sequence could be assigned to the particular test person without additional prior information. In particular, the neutral profiles appeared to be highly consistent intra-individually (across the gait cycles as well as speed levels), but substantially different between test persons. A full discrimination of test persons was achieved using the neutral profiles with respect to flexion/extension data. Based on this, these signals can be considered as individual characteristics for the particular test persons.     

Underwater audiogram of the California sea lion by the conditioned vocalization technique

Conditioning techniques were developed demonstrating that pure tone frequencies under water can exert nearly perfect control over the underwater click vocalizations of the California sea lion (Zalophus californianus). Conditioned vocalizations proved to be a reliable way of obtaining underwater sound detection thresholds in Zalophus at 13 different frequencies, covering a frequency range of 250 to 64,000 Hz. The audiogram generated by these threshold measurements suggests that under water, the range of maximal sensitivity for Zalophus lies between one and 28 kHz with best sensitivity at 16 kHz. Between 28 and 36 kHz there is a loss in sensitivity of 60 dB/octave. However, with relatively intense acoustic signals (> 38 dB re 1 μb underwater), Zalophus will respond to frequencies at least as high as 192 kHz. These results are compared with the underwater hearing of other marine mammals.     

Logical rules of visual brain: From anatomy through neurophysiology to cognition

Humans can easily recognize objects as complex as faces even if they have not seen them in such conditions or context before. It seems that perceptually we are insensitive to the exact properties of an object’s parts but the same parts in different configurations or contexts may introduce contradictory effects. From a computational point of view, we are often insensitive to changes of some symbols, but the same symbols may lead to different classification of the same object. In present work we are looking for the anatomical and neurophysiological basis of these perceptual effects. We describe interactions between parts and their configurations in different areas of the visual brain on the basis of a single cell electrophysiological activity in the thalamus, and cortical areas V1 and V4. Our model is based on feedforward (FF) and feedback (FB) interactions between these areas. In the retina and thalamus simple light spots are classified, V1 is the first area extracting edge orientation and V4 is the first area sensitive to simple shapes. The FF pathways combine properties extracted in each area into hypothetical objects. Area V1 presents concepts of orientations, while area V4 presents concepts of a simple shape. The FB pathways are responsible for comparison of the learned concepts with extracted object’s properties – they form predictions. In each area structure related predictions are tested against hypothesis. We formulate a theory in which different visual stimuli are described through their condition attributes: responses in LGN, V1, and V4 neurons are divided into several ranges and are treated as decision attributes. Applying rough set theory [Pawlak, Z. (1991). Rough sets – theoretical aspects of reasoning about data. Boston, London, Dordrecht: Kluwer Academic Publishers] we have divided our stimuli into area dependent equivalent classes. We propose that relationships between decision rules in each area are determined by two different logical rules: “driver logical rule” of FF and “modulator logical rule” of FB pathways. These interactions are proposed to be a neurophysiological basis of the object classification.     

Low-noise microvolt level calibrator for measurement of performance of biosignal recording systems

A calibrator, the noise level of which is below the noise level generated in the preamplifier system, was needed for testing and development of a multichannel recording system. A multichannel preamplifier head assembly was used for recording cortical, subcortical, and cerebellar slow potentials and multiunit activity in freely moving cats and restrained rabbits. An inexpensive, battery-powered, lownoise voltage signal generator for calibration of the preamplifiers is described. The circuit provides a square-wave output at a frequency of 10 or 1000 Hz, and the peak-to-peak (p-p) amplitude can be selected at 10, 100, or 1000µV. The measured output noise of the calibrator is below 2µV (p-p, 0.1–6000 Hz). The frequency and amplitude values can be easily adapted for different purposes by changing a few component values. An amplified (gain 1,000×) test output for direct oscilloscope monitoring is included in the calibrator circuit.     

Coordination of Grip Configurations as a Function of Force Output

In this investigation, the authors examined the coordination and control of force production by the digits of the hand as a function of criterion force level and grip configuration. Each adult participant (N = 6: 3 men and 3 women) was required to place the thumb and a finger (or fingers) upon load cells that were fixed to a grasping apparatus that was clamped to a table. In the task, participants had to match a criterion continuous constant total force level displayed on a computer screen. There were 10 trials at each grip configuration and criterion force level combination on each of 3 consecutive days. The results showed that (a) different grip configurations minimized error at each force level; (b) there was a specific digit pairing within a given grip configuration that produced the highest correlation of force output; (c) the correlation between the force output of digits generally increased at higher force levels; (d) error was reduced at each force level and grip configuration over the practice period; and (e) the organization of the force output of each digit varied as a function of digit, force level, grip configuration, and practice. The findings are consistent with the hypothesis that coordination of the digits in prehension is reflective of an adaptive, task-specific solution that is modified with practice.     

Principal postural acceleration and myoelectric activity: Interrelationship and relevance for characterizing neuromuscular function in postural control

One approach to investigating sensorimotor control is to assess the accelerations that produce changes in the kinematic state of the system. When assessing complex whole-body movements, structuring the multi-segmental accelerations is important. A useful structuring can be achieved through a principal component analysis (PCA) performed on segment positions followed by double-differentiation to obtain “principal accelerations” (PAs). In past research PAs have proven sensitive to altered motor control strategies, however, the interrelationship between PAs and muscle activation (surface electromyography, sEMG) have never been determined. The purpose of the current study was therefore to assess the relationship between PAs and sEMG signals recorded from muscles controlling the ankle joint during one-leg standing trials. It was hypothesized that medium correlation should be observed when accounting for neurophysiologic latencies (electro-mechanical delay). Unipedal balancing on a level-rigid ground was performed by 25 volunteers. sEMG activities were recorded from the tibialis anterior, peroneus longus, gastrocnemius medialis, and soleus muscles of the stance leg. The first eight PA-time series were determined from kinematic marker data. Then, a cross-correlation analysis was performed between sEMG and PA time series. We found that peak correlation coefficients for many participants aligned at time delays between 0.116 and 0.362 s and were typically in the range small to medium (|r| = 0.1 to 0.6). Thus, the current study confirmed a direct association between many principal accelerations PA(t) and muscle activation signals recorded from four muscles crossing the ankle joint complex. The combined analysis of PA and sEMG signals allowed exploring the neuromuscular function of each muscle in different postural movement components.     

Limulus psychophysics: Increment threshold

Prior temporal summation work had indicated that the sensory code for certain behaviors (in bothLimulus and humans) can be understood if one suggests that the central nervous system analyzes the integral of the photoreceptor potential. An independent test of this suggestion is available because (inLimulus) the physiological increment threshold function obtained from the receptor potential integral is inflected, whereas that obtained from the initial transient peak of the receptor potential is not. The behavioral increment threshold function was measured inLimulus and found to be inflected. Fechner’s scaling assumption (that equally detectable stimulus increments are mediated by sensory signals of equal size) was supported by the fact that a theoretical function, which was calculated from the receptor integral intensity-response function by using Fechner’s scaling assumption, was able to fit the behavioral increment threshold function quite well. Furthermore, the variability of the behavioral data was proportional to the receptor integral variability. A seasonal effect was observed: Fall animals were more sensitive and had a higher criterion than winter animals. These findings permit the specification of the rerceptor potential that mediates this particular behavior at threshold: It has a steady-state amplitude of 7 mV in winter and 16 mV in fall. Taken in conjunction with the results of earlier temporal summation work indicating that the threshold receptor potential is 4.5 sec long, this specification implies that at least some behaviors are mediated by large, long sensory signals, which have properties very different from those of small, short signals, particularly with regard to both linearity and their relative dependence on time vs. energy.     

Coordination of grip configurations as a function of force output

In this investigation, the authors examined the coordination and control of force production by the digits of the hand as a function of criterion force level and grip configuration. Each adult participant (N = 6: 3 men and 3 women) was required to place the thumb and a finger (or fingers) upon load cells that were fixed to a grasping apparatus that was clamped to a table. In the task, participants had to match a criterion continuous constant total force level displayed on a computer screen. There were 10 trials at each grip configuration and criterion force level combination on each of 3 consecutive days. The results showed that (a) different grip configurations minimized error at each force level; (b) there was a specific digit pairing within a given grip configuration that produced the highest correlation of force output; (c) the correlation between the force output of digits generally increased at higher force levels; (d) error was reduced at each force level and grip configuration over the practice period; and (e) the organization of the force output of each digit varied as a function of digit, force level, grip configuration, and practice. The findings are consistent with the hypothesis that coordination of the digits in prehension is reflective of an adaptive, task-specific solution that is modified with practice.     

Perceptual interference and facilitation with auditory imagery

It has been claimed both that (1) imagery selectivelyinterferes with perception (because images can be confused with similar stimuli) and that (2) imagery selectivelyfacilitates perception (because images recruit attention for similar stimuli). However, the evidence for these claims can be accounted for without postulating either image-caused confusions or attentional set. Interference could be caused by general and modality-specific capacity demands of imaging, and facilitation, by image-caused eye fixations. The experiment reported here simultaneously tested these two apparently conflicting claims about the effect of imagery on perception in a way that rules out these alternative explanations. Subjects participated in a two-alternative forced-choice auditory signal detection task in which the target signal was either the same frequency as an auditory image or a different frequency. The possible effects of confusion and attention were separated by varying the temporal relationship between the image and the observation intervals, since an image can only be confused with a simultaneous signal. We found selective facilitation (lower thresholds) for signals of the same frequency as the image relative to signals of a different frequency, implying attention recruitment; we found no selective interference, implying the absence of confusion. These results also imply that frequency information is represented in images in a form that can interact with perceptual representations.     

Refuting the unfolding-argument on the irrelevance of causal structure to consciousness

The unfolding argument (UA) was advanced as a refutation of prominent theories, which posit that phenomenal experience is determined by patterns of neural activation in a recurrent (neural) network (RN) structure. The argument is based on the statement that any input–output function of an RN can be approximated by an “equivalent” feedforward-network (FFN). According to UA, if consciousness depends on causal structure, its presence is unfalsifiable (thus non-scientific), as an equivalent FFN structure is behaviorally indistinguishable with regards to any behavioral test. Here I refute UA by appealing to computational theory and cognitive-neuroscience. I argue that a robust functional equivalence between FFN and RN is not supported by the mathematical work on the Universal Approximator theorem, and is also unlikely to hold, as a conjecture, given data in cognitive neuroscience; I argue that an equivalence of RN and FFN can only apply to static functions between input/output layers and not to the temporal patterns or to the network’s reactions to structural perturbations. Finally, I review data indicating that consciousness has functional characteristics, such as a flexible control of behavior, and that cognitive/brain dynamics reveal interacting top-down and bottom-up processes, which are necessary for the mediation of such control processes.     

Independent control of dual video subsystems on the IBM PC and compatibles

Two methods for generating video output on multiple video monitors are described. The first method involves splitting the signal from a single video adaptor card-so that multiple video monitors may be attached. Although this method is simple and relatively cost-effective, it is limited to adaptors that produce only digital video signals, thus precluding the use of VGA systems and composite displays. The second method involves the installation and programming of video adaptors: Two sample programs, which control a secondary adaptor by means of either BIOS routines or direct commands via C code, are described. Although more complex, this second method allows output to each display to be controlled independently. Furthermore, output to one screen may consist of graphics information while output to the second screen consists of text. Together, both methods can be used to create an experimental system composed of multiple data-collection stations and an independent experimenter console.     

Locus of the redundant-signals effect in bimodal divided attention: A neurophysiological analysis

We reanalyzed the data from the study of Lamarre, Busby, and Spidalieri (1983). In that study, the activity of single neurons in area 4 of the motor cortex was recorded during a bimodal detection task in which a monkey (Macaca mulatta)had to respond as quickly as possible to a visual or an auditory signal or to both (redundant trials). Manual responses on redundant trials were speeded by the presence of both signals, as is typically found. The times between signal onsets and the first changes in neuronal activity were also speeded by redundant signals, but there was no difference between redundant-signals and single-signal trials in the time between the change in neuronal activity and movement onset. These results suggest that late motor processes are not speeded by redundant signals in bimodal detection tasks.     

Hemispheric refractoriness and control of reaction time

Experiments are described which attempt to assess the relative efficiency of the hemispheres and their relationship in performance on complex RT tasks. A divided visual field method was used to direct signals to the temporal or nasal retinae of each eye thus passing information to separate hemispheres. A comparison of the separate response times was used to assess the relative efficiency of each hemisphere but significant differences were not observed. This suggests that each may be the equal of the other in organizing simple responses. A method was used to examine more complex RT by presenting the subject with two simultaneous signals for response. When pairs of signals are directed to separate hemispheres, response times are at their lowest value. When signals are directed to separate hemispheres through the same eye, a significant increase in RT occurs. A source of mutual interference appears to exist at the level of the eye. Response times are extended to their greatest value, however, when both signals are directed to the same hemisphere. This block to function has been described as “hemispheric refractoriness”, and is different for the two hemispheres. While each show a distinct block to function the extent of this is greater in the right or minor hemisphere than it is in the left or major hemisphere.     

Categories and boundaries in speech and music*

Perceptual categories and boundaries arise when Ss respond to continuous variation on a physical dimension in a discontinuous fashion. It is more difficult to discriminate between members of the same category than to discriminate between members of different categories, even though the amount of physical difference between both pairs is the same. Speech stimuli have been the sole class of auditory signals to yield such perception; for example, each different consonant phoneme serves as a category label. Experiment I demonstrates that categories and boundaries occur for both speechand nonspeech stimuli differing in rise time. Experiment II shows that rise time cues categorical differences in both complex and simple nonspeech waveforms. Taken together, these results suggest that certain aspects of speech perception are intimately related to processes and mechanisms exploited in other domains. The many categories in speech may be based on categories that occur elsewhere in auditory perception.     

Physiological indicators of driver workload during car-following scenarios and takeovers in highly automated driving

This driving simulator study, conducted as a part of Horizon2020-funded L3Pilot project, investigated how different car-following situations affected driver workload, within the context of vehicle automation. Electrocardiogram (ECG) and electrodermal activity (EDA)-based physiological metrics were used as objective indicators of workload, along with self-reported workload ratings. A total of 32 drivers were divided into two equal groups, based on whether they engaged in a non-driving related task (NDRT) during automation (SAE Level 3) or monitored the drive (SAE Level 2). Drivers in both groups were exposed to two counterbalanced experimental drives, lasting ∼ 18 min each, of Short (0.5 s) and Long (1.5 s) Time Headway conditions during automated car-following (ACF), which was followed by a takeover that happened with or without a lead vehicle. Results showed that driver workload due to the NDRT was significantly higher than both monitoring the drive during ACF and manual car-following (MCF). Furthermore, the results indicated that a lead vehicle maintain a shorter THW can significantly increase driver workload during takeover scenarios, potentially affecting driver safety. This warrants further research into understanding safe time headway thresholds to be maintained by automated vehicles, without placing additional cognitive or attentional demands on the driver. Our results indicated that ECG and EDA signals are sensitive to variations in workload, which warrants further investigation on the value of combining these two signals to assess driver workload in real-time, to help future driver monitoring systems respond appropriately to the limitations of the driver, and predict their performance in the driving task, if and when they have to resume manual control of the vehicle after a period of automated driving.