Showing papers on "Time perception published in 1998"

Where and when to pay attention: the neural systems for directing attention to spatial locations and to time intervals as revealed by both PET and fMRI.

Abstract: Although attention is distributed across time as well as space, the temporal allocation of attention has been less well researched than its spatial counterpart. A temporal analog of the covert spatial orientation task [Posner MI, Snyder CRR, Davidson BJ (1980) Attention and the detection of signals. J Exp Psychol Gen 109:160-174] was developed to compare the neural systems involved in directing attention to spatial locations versus time intervals. We asked whether there exists a general system for allocating attentional resources, independent of stimulus dimension, or whether functionally specialized brain regions are recruited for directing attention toward spatial versus temporal aspects of the environment. We measured brain activity in seven healthy volunteers by using positron emission tomography (PET) and in eight healthy volunteers by using functional magnetic resonance imaging (fMRI). The task manipulated cued attention to spatial locations (S) and temporal intervals (T) in a factorial design. Symbolic central cues oriented subjects toward S only (left or right), toward T only (300 msec or 1500 msec), toward both S and T simultaneously, or provided no information regarding S or T. Subjects also were scanned during a resting baseline condition. Behavioral data showed benefits and costs for performance during temporal attention similar to those established for spatial attention. Brain-imaging data revealed a partial overlap between neural systems involved in the performance of spatial versus temporal orientation of attention tasks. Additionally, hemispheric asymmetries revealed preferential right and left parietal activation for spatial and temporal attention, respectively. Parietal cortex was activated bilaterally by attending to both dimensions simultaneously. This is the first direct comparison of the neural correlates of attending to spatial versus temporal cues.

Cortical networks underlying mechanisms of time perception

Abstract: Precise timing of sensory information from multiple sensory streams is essential for many aspects of human perception and action. Animal and human research implicates the basal ganglia and cerebellar systems in timekeeping operations, but investigations into the role of the cerebral cortex have been limited. Individuals with focal left (LHD) or right hemisphere (RHD) lesions and control subjects performed two time perception tasks (duration perception, wherein the standard tone pair interval was 300 or 600 msec) and a frequency perception task, which controlled for deficits in time-independent processes shared by both tasks. When frequency perception deficits were controlled, only patients with RHD showed time perception deficits. Time perception competency was correlated with an independent test of switching nonspatial attention in the RHD but not the LHD patients, despite attention deficits in both groups. Lesion overlays of patients with RHD and impaired timing showed that 100% of the patients with anterior damage had lesions in premotor and prefrontal cortex (Brodmann areas 6, 8, 9, and 46), and 100% with posterior damage had lesions in the inferior parietal cortex. All LHD patients with normal timing had damage in these same regions, whereas few, if any, RHD patients with normal timing had similar lesion distributions. These results implicate a right hemisphere prefrontal-inferior parietal network in timing. Time-dependent attention and working memory functions may contribute to temporal perception deficits observed after damage to this network.

Temporal processing in the basal ganglia

Abstract: This study investigated the role of the basal ganglia in timing operations. Nondemented, medicated Parkinson's disease (PD) patients and controls were tested on 2 motor-timing tasks (paced finger tapping at a 300- or 600-ms target interval), 2 time perception tasks (duration perception wherein the interval between the standard tone pair was 300 or 600 ms), and 2 tasks that controlled for the auditory processing (frequency perception) demands of the time perception task and the movement rate (rapid tapping) in the motor-timing task. Using A.M. Wing and A.B. Kristofferson's (1973) model, the total variability in motor timing was partitioned into a clock component, which reflects central timekeeping operations, and a motor delay component, which estimates random variability due to response implementation processes. The PD group was impaired at both target intervals of the time perception and motor-timing tasks. Impaired motor timing was due to elevated clock but not motor delay variability. The findings implicate the basal ganglia and its thalamocortical connections in timing operations.

Analysis of temporal structure in sound by the human brain.

Abstract: For over a century, models of pitch perception have been based on the frequency composition of the sound. Pitch phenomena can also be explained, however, in terms of the time structure, or temporal regularity, of sounds. To locate the mechanism for the detection of temporal regularity in humans, we used functional imaging and a 'delay-and-add' noise, which activates all frequency regions uniformly, like noise, but which nevertheless produces strong pitch perceptions and tuneful melodies. This stimulus has temporal regularity that can be systematically altered. We found that the activity of primary auditory cortex increased with the regularity of the sound. Moreover, a melody composed of delay-and-add 'notes' produced a distinct pattern of activation in two areas of the temporal lobe distinct from primary auditory cortex. These results suggest a hierarchical analysis of time structure in the human brain.

Directed attention prolongs the perceived duration of a brief stimulus

Abstract: Stelmach, Herdman, and McNeil (1994) suggested recently that the perceived duration for attended stimuli is shorter than that for unattended ones. In contrast, the attenuation hypothesis (Thomas & Weaver, 1975) suggests the reverse relation between directed attention and perceived duration. We conducted six experiments to test the validity of the two contradictory hypotheses. In all the experiments, attention was directed to one of two possible stimulus sources. Experiments 1 and 2 employed stimulus durations from 70 to 270 msec. A stimulus appeared in either the visual or the auditory modality. Stimuli in the attended modality were rated as longer than stimuli in the unattended modality. Experiment 3 replicated this finding using a different psychophysical procedure. Experiments 4-6 showed that the finding applies not only to stimuli from different sensory modalities but also to stimuli appearing at different locations within the visual field. The results of all six experiments support the assumption that directed attention prolongs the perceived duration of a stimulus.

Effect of deviations from temporal expectations on tempo discrimination of isochronous tone sequences.

Abstract: The effect of deviations from temporal expectations on tempo discrimination was studied in 3 experiments using isochronous auditory sequences. Temporal deviations consisted of advancing or delaying the onset of a comparison pattern relative to an "expected" onset, defined by an extension of the periodicity of a preceding standard pattern. An effect of onset condition was most apparent when responses to faster and slower comparison patterns were analyzed separately and onset conditions were mixed. Under these conditions, early onsets produced more "faster" judgments and lower thresholds for tempo increases, and late onsets produced more "slower" judgments and lower thresholds for tempo decreases. In another experiment, pattern tempo had a similar effect: Fast tempos led to lower thresholds for tempo increases and slow tempos led to lower thresholds for tempo decreases. Findings support oscillator-based approaches to time discrimination.

Functional dissociation of the prefrontal cortex and the hippocampus in timing behavior.

Abstract: Using the peak procedure, rats with aspiration lesions to the medial prefrontal cortex (PFC) or the hippocampus were tested for the acquisition of timing behavior and temporal memory. After surgery, rats were 1st trained to discriminate a 40-s interval and then tested for temporal memory with gap trials. Results indicated that lesions to the medial PFC disrupted the acquisition of timing behavior. Medial PFC animals needed significantly more trials to reach criterion, and their temporal discrimination function was less uniform and steep, indicating a general deficit in timing ability. In hippocampal rats, the ability to estimate the duration of the discriminative stimulus was unaffected by the lesion. It was concluded that the hippocampus is not necessary for the acquisition of timing behavior in this task. Gap trials failed to produce a deficit in the memory for temporal events for either lesion. Thus, it was further concluded that neither the medial PFC nor the hippocampus is necessary for the memory of temporal events.

Obligatory "expectations" of expressive timing induced by perception of musical structure.

Abstract: Previous research has shown that, in a task requiring the detection of local deviations from mechanically precise timing in music, the relative detectability of deviations in different positions is closely related to the typical expressive timing pattern musicians produce when playing the music. This result suggests that listeners expect to hear music expressively timed and compensate for the absence of expressive timing. Three new detection experiments shed additional light on the nature of these timing expectations in musically trained listeners. Experiment 1 shows that repeated exposure to an atypically (but not unmusically) timed performance leaves listeners' timing expectations unaffected. Experiment 2 demonstrates that the expectations do not manifest themselves when listeners merely imagine the music in synchrony with a click track. Experiment 3, however, shows that the timing expectations are fully operational when the click track is superimposed on the music. These results reveal timing “expectations” to be an obligatory consequence of the ongoing auditory perception of musical structure.

Time perception and time estimation in depressive patients

Abstract: Subjective time-experience and objective time-estimation were examined in 20 endogenous, 20 neurotic depressives, and 15 healthy volunteers. Subjective experience of past and anticipated future time was more extended in both depressive groups than in healthy controls. Objective time estimation differed between depressives and controls concerning relatively long time spans whereas very short time spans were correctly estimated also by depressives. There were no significant differences between endogenous and neurotic depressives. The perception of extended time normalized during treatment. The depressives' time perception, differences correlated with the extent of depressive psychopathological symptoms and--to a lesser degree--with retardation. The findings support the hypotheses of anthropological phenomenology concerning disturbed time perception and estimation in depressives. Amelioration of experienced time-extension in intentionally structured time spans compared to empty time spans suggests psychotherapeutic consequences in the sense of Lewinsohn.

Categorical Rhythm Perception as a Result of Unilateral Assimilation in Time-Shrinking

Abstract: In previous studies, we established an illusion of time perception that we called time-shrinking: an empty time interval, immediately preceded by a slightly shorter time interval, is underestimated. In the first experiment of the present study, we examined the perceived duration not only of the second interval (t2), but also of the first interval (tl). The empty time intervals tl and t2, making a total duration of 90,180, 360, or 720 ms, were presented such that the time ratio between them changed systematically. The points of subjective equality of tl and t2 were established by the method of adjustment. In the patterns typically susceptible to timeshrinking, that is, in which t2 was underestimated, tl was perceived almost vertically. In the second experiment, listeners had to bisect an empty duration of 180 ms, marked by sound bursts. The bisecting sound marker was positioned closer to the initial marker than to the final one. Thus, tl had to be shorter than t2 in order for a regular pattern to be perceived. In the third experiment, just-noticeable forward and backward displacements of the middle sound marker were measured by a transformed updown method. The prediction that the interval of uncertainty was closer to the initial than to the final sound marker was confirmed. The three experiments demonstrated the existence of unilateral temporal assimilation, and it is argued that this perceptual mechanism causes a category of 1:1 rhythms, despite a considerable change in temporal ratio between two contiguous time intervals.