Trevor B. Penney

Differential effects of auditory and visual signals on clock speed and temporal memory.

The effects of signal modality on duration classification in college students were studied with the duration bisection task. When auditory and visual signals were presented in the same test session and shared common anchor durations, visual signals were classified as shorter than equivalent duration auditory signals. This occurred when auditory and visual signals were presented sequentially in the same test session and when presented simultaneously but asynchronously. Presentation of a single modality signal within a test session, or both modalities but with different anchor durations did not result in classification differences. The authors posit a model in which auditory and visual signals drive an internal clock at different rates. The clock rate difference is due to an attentional effect on the mode switch and is revealed only when the memories for the short and long anchor durations consist of a mix of contributions from accumulations generated by both the fast auditory and slower visual clock rates. When this occurs auditory signals seem longer than visual signals relative to the composite memory representation.

Scalar expectancy theory and peak-interval timing in humans

The properties of the internal clock, temporal memory, and decision processes used to time short durations were investigated. The peak-interval procedure was used to evaluate the timing of 8-, 12-, and 21-s intervals, and analyses were conducted on the mean response functions and on individual trials. A distractor task prevented counting, and visual feedback on accuracy and precision was provided after each trial. Mean response distributions were (a) centered at the appropriate real-time criteria, (b) highly symmetrical, and (c) scalar in their variability. Analysis of individual trials indicated more memory variability relative to response threshold variability. Taken together, these results demonstrate that humans show the same qualitative timing properties that other animals do, but with some quantitative differences.

Brain Responses to Segmentally and Tonally Induced Semantic Violations in Cantonese

The present event-related potential (ERP) study examined the role of tone and segmental information in Cantonese word processing. To this end, participants listened to sentences that were either semantically correct or contained a semantically incorrect word. Semantically incorrect words differed from the most expected sentence completion at the tone level, at the segmental level, or at both levels. All semantically incorrect words elicited an increased frontal negativity that was maximal 300 msec following word onset and an increased centroparietal positivity that was maximal 650 msec following word onset. There were differences between completely incongruous words and the other two violation conditions with respect to the latency and amplitude of the ERP effects. These differences may be due to differences in the onset of acoustic deviation of the presented from the expected word and different mechanisms involved in the processing of complete as compared to partial acoustic deviations. Most importantly, however, tonally and segmentally induced semantic violations were comparable. This suggests that listeners access tone and segmental information at a similar point in time and that both types of information play comparable roles during word processing in Cantonese.

Event related brain potentials and illusory memories: the effects of differential encoding

This study investigates event related potentials (ERP) elicited by true and false recognition using words from different semantic categories. In Experiment 1, ERPs for true and false recognition were more positive than for correctly rejected NEW words starting around 300 ms after test word presentation (old/new ERP effects). ERP waveforms for true and false recognition revealed equal early (300-500 ms) fronto-medial old/new ERP effects, reflecting similar familiarity processes, but smaller parietal old/new ERP effects (500-700 ms) for false relative to true recognition, suggesting less active recollection. Interestingly, a subsequent performance based group comparison showed equivalent old/new ERP effects for true and false recognition for participants with high rates of false recognition. In contrast, false recognition failed to elicit an old/new ERP effect in a group with low false recognition rates. To examine whether this between group difference was driven by the differential use of information that studied words and semantically related non studied test words (LURE) have in common (conceptual similarity), we manipulated encoding strategy in Experiment 2. When encoding focused on conceptual similarity, comparable ERP-effects for true and false recognition were obtained, suggesting that both forms of recognition were equally based on familiarity and recollection processes. Conversely, when encoding was focused on item specific features, differences in brain activity for true and false recognition were obtained. The ERP data indicate that, in addition to the false recognition rate, strategic processes during encoding, such as processing conceptual features, are an important factor in determining electrophysiological differences between true and false recognition.

The Habenula Prevents Helpless Behavior in Larval Zebrafish

Animals quickly learn to avoid predictable danger. However, if pre-exposed to a strong stressor, they do not display avoidance even if this causes continued contact with painful stimuli [1, 2]. In rodents, lesioning the habenula, an epithalamic structure that regulates the monoaminergic system, has been reported to reduce avoidance deficits caused by inescapable shock [3]. This is consistent with findings that inability to overcome a stressor is accompanied by an increase in serotonin levels [4]. However, other studies conclude that habenula lesions cause avoidance deficits [5, 6]. These contradictory results may be caused by lesions affecting unintended regions [6]. To clarify the role of the habenula, we used larval zebrafish, whose transparency and amenability to genetic manipulation enables more precise disruption of cells. We show that larval zebrafish learn to avoid a light that has been paired with a mild shock but fail to do so when pre-exposed to inescapable shock. Photobleaching of habenula afferents expressing the photosensitizer KillerRed causes a similar failure in avoidance. Expression of tetanus toxin in dorsal habenula neurons is sufficient to prevent avoidance. We suggest that this region may signal the ability to control a stressor, and that its disruption could contribute to anxiety disorders.

Contingent negative variation and its relation to time estimation: a theoretical evaluation

The relation between the contingent negative variation (CNV) and time estimation is evaluated in terms of temporal accumulation and preparation processes. The conclusion is that the CNV as measured from the electroencephalogram (EEG) recorded at fronto-central and parietal-central areas is not a direct reflection of the underlying interval timing mechanism(s), but more likely represents a time-based response preparation/decision-making process.

Categorical Scaling of Duration Bisection in Pigeons (Columba livia), Mice (Mus musculus), and Humans (Homo sapiens)

A fundamental assumption underlying research in translational neuroscience is that animal models represent many of the same neurocognitive mechanisms and decision processes used by humans. Clear demonstrations of such correspondences will be crucial to the discovery of the neurobiological underpinnings of higher-level cognition. One domain likely to support fruitful comparisons is interval timing, because humans and other animals appear to share basic similarities in their ability to discriminate the durations of events in the seconds-to-minutes range. Here, we report that in a duration-bisection procedure using a series of anchor durations ranging from 2 through 5 s, pigeon, mouse, and human subjects classified a given signal duration as subjectively shorter than an adjacent, physically shorter signal duration when the two durations lay on opposite sides of a putative category boundary. These bisection reversals provide strong evidence for continuity of temporal cognition across a wide range of vertebrate species.

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. Johns, 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 subjects 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

Event-related optical imaging reveals the temporal dynamics of right temporal and frontal cortex activation in pre-attentive change detection

The mismatch negativity (MMN) is a pre-attentive brain response to auditory environmental change. Temporal and frontal cortex generators of pre-attentive change detection have been proposed based on source localization of event-related potentials (ERP), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI) studies. The temporal cortex generators are believed to underlie change detection, whereas the frontal cortex generators are thought to subserve reorientation of attention in response to change. The present study used the event-related optical signal (EROS), an imaging technique that is sensitive to activity related changes in the light scattering properties of neurons, to investigate the pre-attentive brain response to stimulus omissions. The stimulus train comprised 10 ms tone pips presented with a stimulus onset asynchrony (SOA) of 84 ms. Occasional tone omissions elicited a significant increase in right superior temporal gyrus (STG) activity 140 ms after the omitted stimulus, followed 60 ms later by right inferior frontal gyrus (IFG) activity. This result provides support for a temporal-frontal cortical network that underlies pre-attentive change detection.

The Role of Visual and Auditory Temporal Processing for Chinese Children with Developmental Dyslexia.

This study examined temporal processing in relation to Chinese reading acquisition and impairment. The performances of 26 Chinese primary school children with developmental dyslexia on tasks of visual and auditory temporal order judgement, rapid naming, visual-orthographic knowledge, morphological, and phonological awareness were compared with those of 26 reading level ability controls (RL) and 26 chronological age controls (CA). Dyslexic children performed worse than the CA group but similar to the RL group on measures of accurate processing of auditory and visual-order stimuli, rapid naming, morphological awareness, and phonological awareness and a minority performed worse on the two temporal processing tasks. However, hierarchical regression analyses revealed that visual but not auditory temporal processing contributed unique variance to Chinese character recognition even with other cognitive measures controlled, suggesting it may be as important a correlate of reading ability in Chinese as in alphabetic scripts.