Signal Modality Research Articles

Canine Communication

Communication occurs when one individual, the sender, produces a signal that alters the behavior of another individual, the receiver. The signal can provide broadcast information about species and individual identity or transmitted information, in which the sender effects a change in the receiver's behavior. To reduce ambiguity, signals have evolved to be conspicuous, redundant, and stereotypic. These features allow communication signals to be produced by senders and perceived and acted upon appropriately by receivers, both conspecific and heterospecific. The modality of the communication signal can be visual, olfactory, or acoustic. Visual signals can be adjusted rapidly for response during interactions between individuals at close or medium range. Examples include displays of relative dominance or submission. Olfactory signals can be used for individual, sex, or group identity at close range during greetings and assessments of individuals. Excretory products can be used for olfactory communication over long distances and for long periods of time. Acoustic signals can be adjusted rapidly for close- and far-range communication. They do not persist in the environment. For dogs, communication is fundamental to maintaining affiliations, reducing competition, and identifying individuals. These factors are critical to the highly developed social behavior of dogs. In an ultimate sense, dogs have been selectively bred for positive interactions with humans; in a proximate sense, many dogs spend their lives in close social association with humans. For these reasons, many of the signals used by dogs in dog-dog communication are also used in dog-human communication. Veterinarians act as receivers for communication signals when greeting dogs as patients. The information obtained is used to assess the state of arousal and probability of future behavior of the dog so that handling of the animal can be facilitated. The goals are to minimize stress and injury, to successfully complete the treatment program, and to promote the health of the animal.

Anticipatory EMG responses of pericranial muscles in relation to heart rate during a warned simple reaction time task.

Obrist's cardiac-somatic coupling hypothesis predicts a widespread inhibition of heart rate and task-irrelevant muscle activity during expectancy situations. This hypothesis was tested by measuring heart rate and pericranial electromyographic (EMG) activity during a warned simple reaction time task with visual or auditory reaction signals and hand or foot responses. In each of three groups of 24 participants, EMG activity of three different facial, masticatory, or neck muscles was recorded. During the warning interval preceding the presentation of the reaction signal, masticatory and lower facial muscles predominantly showed a gradual inhibition in activity concomitant with heart rate deceleration. In contrast, two upper facial muscles showed increasing activity. Pericranial EMG responses were little affected by reaction signal modality and were independent of responding limb. Greater heart rate deceleration was associated with greater inhibition and weaker facilitation of EMG responses. The results suggest a functional role of inhibitory EMG responses in increasing the perceptual sensitivity to expected signals.

Clonidine-induced antagonism of norepinephrine modulates the attentional processes involved in peak-interval timing.

Duke University The effects of the a2-agonist clonidine and the a2-antagonist idazoxan were studied with emphasis on the attentional mechanisms subserving interval-timing behavior. Administration of clonidine (0.015 mg/kg IP) to rats trained on a 20-s peak-interval (PI) timing procedure caused a rightward shift in peak functions, whereas idazoxan (0.15 mg/kg IP) caused a leftward shift. Rats were also trained on 10-s and 30-s baseline PI timing procedures in combination with the prior-entry and prior-entry reversal versions of this task that produced leftward shifts and rightward shifts relative to baseline training, respectively. Clonidine (0.025 mg/kg IP) produced a rightward shift in peak functions for all of these behavioral procedures. Taken together, these horizontal shifts in the peak functions indicate a decrease (leftward shift) or an increase (rightward shift) in the latency to start the internal clock that is influenced both by the attentional demands of the task and the effective level of brain norepinephrine. Cognitive accounts of information processing divide atten- tion into three major functions: orienting to sensory events, detecting signals for conscious processing, and maintaining an alert state (Posner & Petersen, 1990). The allocation of attention for the detection of signals for conscious processing may result in the subject attending to the expected spatial location, temporal location, or sensory modality of the signal. As a consequence, if the signal is either in an unexpected location or of an unexpected modality, it will not be processed as rapidly. In contrast, if attention is allocated to maintaining a general state of alertness or arousal, then any signal that is of sufficient intensity will engage conscious processing. An information-processing model of interval timing suggests Trevor B. Penney, Department of Psychology, Columbia University; Mark D. Holder, Department of Psychology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada and Department of Psychology, Okanagan University College, Kelowna, British Columbia, Canada; Warren H. Meck, Department of Psychology: Experimental, Duke University. This research was supported in part by a grant from the Natural Sciences and Engineering Research Council of Canada (A1221). Preliminary reports based on this work were presented at the 64th Annual Meeting of the Eastern Psychological Association, Arlington, Virginia (Penney, Holder, M Meck, 1984). Data from human event-related potential (ERP) para- digms (e.g., Gratton et al., 1990) and animal timing tasks (Meck, 1984) suggest that warning signals serve to prime perceptual processing. Consequently, the use of warning signals can be used to influence a subject's expectation of thc stimulus properties (e.g., modality) of a forthcoming signal presentation. Central nervous system norepinephrine (NE) may accentu- ate activity of neurons that are transmitting the presence of significant stimuli and inhibit the activity of other neurons (Kety, 1970). This could be interpreted as an improvement in the signal-to-noise ratio or an enhancement of sclectivc attention. The selective attention hypothesis was initially based on the behavioral results of lesions to the dorsal noradrenergic bundle (DNAB; e.g., Mason, 1980; Robbins, Everitt, Cole, Archer, & Mohammed, 1985). This pathway originates in the pontine nucleus of the locus coeruleus (LC) and provides innervation to the spinal cord, cerebellum, and many forebrain areas including the caudate-putamen (Mason, 1980). The LC may act as an important gating mechanism for 82

Neurons of the cat sensorimotor cortex: Responses related to differentiation of monomodal and heteromodal conditioning signals

Spike responses of the sensorimotor cortex neurons were studied in chronic experiments on cats trained to perform an operant reflex, a placing movement triggered by application of the distant stimuli. The responses recorded under conditions of differentiation of sound tones of various frequencies and of a heteromodal complex (light + tone) from its components were compared. The responses recorded from 125 neurons in 3 animals were analyzed. No neurons selectively responding either to monomodal or to heteromodal signals were found. Forty-five cells responded to positive signals by excitation or inhibition, irrespective of the signal modality. The shortest latencies of these responses were 30 and 40 msec, respectively. When inhibitory stimuli were applied, these neurons either generated much weaker responses, or did not respond at all. A correlation was found between the level of response depression and the level of differentiation of the signals by an animal. These findings allow us to hypothesize that the sensorimotor cortex does participate in differentiation of sensory signals, providing preparation for switching on the motor response after a positive stimulus or suppression of such a response after a negative one.

電撃強度についての情報の有無がラットの摂水反応の抑制におよぼす効果について

Two groups of rats were run to examine the effects of presence and absence of information about shock intensity upon the suppression of rats' licking behavior. Shocks of two different intensities were consistently preceded by signals of two different modalities. The modality of signal and the shock intensity were correlated for Group C (Correlated), but they were not for Group UC (Uncorrelated). Group C clearly evidenced shock intensity discrimination which was manifested in differential conditioned suppression. The baseline licking behavior of rats was suppressed more in Group UC than in Group C, indicating that there was more aversion to the situation in which information about shock intensity was not given than to the situation in which such information was given. The findings were discussed with reference to the results of a computer simulation based on the Rescorla-Wagner model (Rescorla & Wagner, 1972).

Psychophysical determinants of stress in sustained attention.

To date, research on the stress of sustained attention tasks has not explored the extent to which such stress is determined by the psychophysical aspects of the monitored display. In the present study, the effects of the sensory modality of signals (audition and vision) and the background event rate (5 and 40 events/min) on task-induced stress were examined in a vigilance situation. Critical signals for detection were slight changes in stimulus duration. Stress was indexed by motor restlessness and subjective reports of fatigue. Restlessness and subjective fatigue increased dramatically across a 50-min watch in all conditions. Stress effects were most notable in the case of visual monitoring but were unrelated to variations in event rate. Hence, from a psychophysical perspective, the stress of sustained attention seems to be identified more specifically with the sensory modality of signals than with the event rate context in which they appear.

Modality-specific circadian rhythmicities influence mechanisms of attention and memory for interval timing

Two groups of male Sprague-Dawley rats ( n's = 10) were trained to discriminate between 2-s and 8-s signal durations at one of two different phases of a 14:10 light:dark (LD) cycle with lights on at 7:00 am. One group of rats was trained beginning at 8:00 am and the other group of rats was trained beginning at 8:00 pm. Signals were composed of either a 2-s or an 8-s duration of light (6-or 7.5-W lamp onset) or sound (80-dB white noise onset) presented with equal probability in a random order during a 2-h session. Five intermediate signal durations, in addition to the two anchor points, were presented by means of the bisection method with discrete trials separated by a random-interval 45-s intertrial interval (ITI). After baseline response functions for both auditory and visual signals were obtained at the two training phases, test sessions were conducted at eight different times during the LD cycle. These test sessions were conducted in order to determine whether any of the psychological processes involved in the discrimination of signal duration in the seconds to minutes' range exhibit a cirdadian rhythm. The results obtained from the test stage revealed no circadian rhythmicity in clock speed (Λ) for either signal modality; whereas, the variability or temporal memory for sound signals ( γ K ∗ | S ) and the probability of attention to light signals ( p( A) | L)—as estimated from the application of a scalar expectancy model of temporal bisection—showed circadian rhythmicities that interacted with the circadian phase of initial baseline training.

Effects of Signal Modality on Signal-Controlled Responses in Pigeons

Effects of Signal Modality on Signal-Controlled Responses in Pigeons

Premotor cortex neurons in macaques: activity before distal and proximal forelimb movements

Single unit activity was examined in the premotor cortex of three awake, behaving macaque monkeys. Premotor cortex (PM) neurons were found to be active in association with a movement involving specifically the distal forelimb. Other PM neurons were active in relation to more proximal forelimb movements. The spatial distribution of neurons related to distal movements differed from that of neurons related to proximal forelimb movements, the former being focused at a postarcuate region near the genu of the arcuate sulcus and the latter being shifted more posteromedially. The distal movement was triggered by one of the three sensory signals: visual, auditory, and vibrotactile. Of 190 PM neurons related to the distal forelimb movements, 123 (65%) showed similar premovement activity changes irrespective of the modality of the triggering signal. However, a number of neurons (35%) responded preferentially to one or two of the three signals. The modality-specific activity before movements distinguishes PM from the caudally adjacent primary motor cortex.

Signal intensity, task context, and auditory-visual interactions.

A study is reported of the effect of signal intensity on immediate cross-modal bias between vision and audition. Each signal was presented at high or low intensity, giving rise to four conditions. The study also dealt with the effectiveness of instructions and task context in directing attention. Two kinds of task (pointing) contexts were compared: a constant or unimodal context in which the modality of the target signal was the same throughout a session, and a bimodal one in which it changed from trial to trial. In both conditions subjects were instructed that the signals might come from the same or from different positions, depending on the trial. For visual bias of audition the results show that a signal with high intensity was more biasing and less biased than one with low intensity. Auditory bias of vision did not reach significance in any of the four intensity conditions. Type of task context had no effect on the extent of bias, suggesting that a constant-task (unimodal) context was no more effective in directing attention than instructions alone.

Postreinforcement signal processing.

Postreinforcement signal processing by rats was demonstrated in six experiments that used a discrete-trials choice procedure. Experiment 1 assessed the extent to which rats are able to transfer knowledge about associations between postreinforcement signal durations and choice responses to conditions where a particular signal duration preceded the opportunity to make a choice response. In Experiment 2 the generality of the transfer effect was demonstrated by using both signal duration and signal modality as relevant stimulus attributes for the postreinforcement signals. The role of the relative durations of the reinforcement-signal gap and the intertrial interval was investigated in Experiment 3. In order to assess the effects of within-trial and between-trial signal relations on the acquisition of a temporal discrimination, both pre-and postreinforcement signals were presented on each trial in Experiments 4 and 5. The effects of pre- and postreinforcement signal relations on the steady-state performance of a temporal bisection task across three different signal ranges were studied in Experiment 6. The conclusion is that rats readily process various stimulus attributes of postreinforcement signals and that relations between postreinforcement signals, choice responses, and prereinforcement signals are major determinants of choice behavior.

SIGNAL MODALITY AND CHOICE BETWEEN SIGNALED AND UNSIGNALED FOOD

Choice between signaled and unsignaled response-independent food schedules was assessed in three experiments using a commitment procedure. In Experiment 1, subjects tested with a 5-s visual signal consistently changed from the signaled to the unsignaled schedule. Changing from the unsignaled to the signaled schedule was observed only occasionally and only at low levels. The same outcome was observed in Experiment 2 with different types of visual signals and with different stimulus combinations identifying the signal period, the signal-absent period, and the unsignaled schedule. In Experiment 3 the visual signal was replaced with an auditory signal for four of the subjects tested in Experiment 2. The subjects then changed from the unsignaled to the signaled schedule or showed a substantial reduction in choice for the unsignaled schedule. The data were assessed using a conditioned-reinforcement interpretation of choice.

Attentional bias between modalities: effect on the internal clock, memory, and decision stages used in animal time discrimination.

Both the presentation of unbalanced stimulus probabilities and the insertion of a predictive cue prior to the signal on each trial apparently induces a strong bias to use a particular stimulus modality in order to select a temporal criterion and response rule. This attentional bias toward one modality is apparently independent of the modality of the stimulus being timed and is strongly influenced by stimulus probabilities or prior warning cues. These techniques may be useful to control trial-by-trial sequential effects that influence a subject's perceptual and response biases when signals from more than one modality are used in duration discrimination tasks. Cross-procedural generality of the effects of attentional bias was observed. An asymmetrical modality effect on the latency to begin timing was observed with both the temporal bisection and the peak procedure. The latency to begin timing light signals, but not the latency to begin timing sound signals, was increased when the signal modality was unexpected. This asymmetrical effect was explained with the assumption that sound signals close the mode switch automatically, but that light signals close the mode switch only if attention is directed to the light. The time required to switch attention is reflected in a reduction of the number of pulses from the pacemaker that enter the accumulator. One positive aspect of this work is the demonstration that procedures similar to those used to study human cognition can be used with animal subjects with similar results. Perhaps these similarities will stimulate animal research on the physiological basis of various cognitive capacities. Animal subjects would be preferred for such physiological experimentation if it were established that they possessed some of the cognitive processes described by investigators of human information processing. One of the negative aspects of this work is that only one combination of modalities was used and variables such as stimulus intensity, stimulus probability, and range of signal durations have not been adequately investigated at present. Future work might test additional combinations of modalities and vary stimulus intensity and stimulus probability within a signal detection theory (SDT) framework to determine the effects of these variables on attentional bias.

Visual and auditory choice reaction times

Choice reaction times are measured for three values of a priori signal probability with three well-practiced observers. Two sets of data are taken with the only difference being the modality of the reaction signal. In one set of conditions it is auditory, in the other, visual. The auditory reaction times are faster than the visual and in addition several other differences are noted. The latency of the errors and correct responses are nearly equal for the auditory data. Error latencies are nearly 30% faster for the visual data. Non-stationary effects, autocorrelation between successive latencies and non-homogeneous distribution of errors, are clearly evident in the visual data, but are small or non-existent in the auditory data. The data are compared with several models of the choice reaction time process but none of the models is completely adequate.

An additive factor analysis of the effects of sleep loss on reaction processes

Two experiments are reported on the mutual relations between the effects of sleep loss and those of signal degradation, S-R compatibility, stimulus intensity and signal modality (auditory vs. visual) on reaction time. Additional variables were time-on-task and time-of-test. The results show a pronounced interaction between the effects of sleep loss and of signal degradation, while additive effects were observed of sleep loss, S-R compatibility, intensity and modality. The interaction was especially pronounced in the afternoon session and increased also as a function of time-on-task. These results suggest that the effects of sleep loss are specifically related to the nature of ongoing cognitive operations rather than affecting a general state of arousal. Furthermore the mutual relations among the reaction variables did not change after sleep loss which argues in favor of the robustness of these relations, and, consequently, of the applicability of linear stage models to reaction processes.

The left-to-right difference in warned reaction times of finger movements

The electromyographic reaction times (RTs) in bilateral finger movements and their left-to-right (l-r) difference were measured in right-handed subjects under conditions of different preparatory intervals (PIs), i.e., periods between warning and command signal. RTs without warning were always longer than warned RTs with PIs of 2–15 sec. Consistent right or left leading l-r differences occurred for PIs ranging from 2 to 6 or 7 sec, but were reduced for longer PIs. Significant l-r differences in warned RTs were consistently maintained regardless of the sensory modality of command signals, and even between separately performed right and left movements. In these tests RTs and their l-r difference changed independently. It is suggested that the warning signal acts on RTs and their l-r difference through two separate facilitatory mechanisms in the central information processing.

Modality-specific effects on discrimination of short empty time intervals.

The ability of human subjects to judge the duration of short empty time intervals was studied in relation to the modality composition of the marker signals. At each trial, a pair of empty intervals was presented by a series of three successive stimuli, and the subject was asked to point out the longer interval of the two. Tone pips and flashes of light were used as the bounding signals. All the possible combinations of auditory and visual stimuli were used, in random order, to delimit pairs of intervals. Performance was found modality-independent when the first two stimuli were of the same modality. Strong response biases were introduced by varying the modality of the first or the second stimulus. Analysis of these biases indicates that memorization of the empty time intervals is affected by the modality of the binding signals.

Attention and reaction times to signals of uncertain modality.

Visual, auditory, and tactile reaction time (RT) signals were used in an a-reaction task. The main independent variable was the predictability of signal modality, which was varied by cuing the relevant modality or modalities before each trial. The response requirement was nondiscriminative with respect to modality. Three experiments showed that (a) RT's were longer when signal modality was uncertain, the more so with three possible modalities than with two; (b) this effect of uncertainty was approximately the same whether varied within subjects or between subjects; and (C) the effect of uncertainty was somewhat smaller on tactile RTs than on visual or auditory RTs. Experiment 4 examined change in this uncertainty effect with practice. The uncertainty effect declined over 11 daily sessions to the point of virtual absence from auditory and tactile RTs but was restored or increase will respect to all three signals following one session of discrimination RTs ("respond if visual, refrain if auditory or tactile"). The results are interpreted as showing that attention can be allocated to sensory modalities and that the implied selective process is concerned with modality "identification," though not in a way consistent with a channel-switching model thereof.

The Foreperiod Effect Revisited

This paper explores four factors which could be important in accounting for the discrepant results which have previously been obtained with respect to the effect of foreperiod duration on reaction time (RT). In some studies a clear effect of foreperiod duration on auditory RT has been found, in contrast to a recent finding that foreperiod duration affected visual RT but not auditory RT. By means of two experiments, the effects of practice, time-on-task, reaction task (a-reaction versus selective reaction) and signal intensity were studied. The latter variable appears to be the principal determinant of the discrepant results in that there is an interaction between signal intensity, foreperiod duration and modality. The results fit the hypothesis that signals beyond a given intensity exert an immediate arousing effect which counteracts the foreperiod effect.

The relation between physical stimulus properties and the effect of foreperiod duration on reaction time.

Seven subjects were used in an experiment on the relation between signal modality and the effect of foreperiod duration (EP) on RT. With visual signals the usually reported systematic increase of RT as a function of FP duration (1, 5 and 15 s) was confirmed; with auditory signals no difference was found between FP's of 1 and 5 s while the effect at 15 s was equivalent to that found at 5 s with the visual signal. The results suggest that besides factors such as time uncertainty the FP effect is also largely dependent on the arousing quality of the signal.