Differences In Response Latencies Research Articles

Age effects on a nonverbal auditory sustained attention task.

A nonverbal auditory test of sustained attention was administered to 20 young and 20 elderly women, screened to ensure good health. Groups were matched for intelligence. Older subjects performed as accurately as younger subjects. Neither group showed increases in response latency as a function of time spent on test. Older subjects took longer to respond than younger subjects, but only for a particular combination of stimulus duration and order of presenting stimulus durations. When subjects were presented long tones first, there was no difference in response latency associated with age or stimulus duration. When short tones were presented first, older subjects were slower than younger subjects in both duration conditions and in response to long tones were slower than all other subjects.

Differential control of hypothalamically elicited flight behavior by the midbrain periaqueductal gray in the cat

The purpose of the present study was to determine the role of the midbrain periaqueductal gray (PAG) and thalamic centrum medianum-parafascicular complex (CM-Pf) in the regulation of hypothalamically elicited flight behavior in the cat. The experimental paradigm involved a comparison of the differences in response latencies between single stimulation of the hypothalamus and concurrent stimulation of the hypothalamus and sites in the PAG or the CM-Pf. Dual stimulation of the ventral and dorsal aspects of the PAG resulted in differential modulation of flight behavior. Stimulation of the dorsal PAG suppressed hypothalamically elicited flight behavior while stimulation of the ventral aspects of the PAG facilitated flight behavior. Facilitation of flight behavior was also found from stimulation of ventral portions of the CM-Pf.

Development of differences in response latencies to right and left visual fields

Robust lateralization developed in right-handed adults who were asked to judge letter pairs as “same” or “different” during 4608 trials. By the end of the first two blocks (768 trials) “same” responses were favored when presented in the RVF (transmitted directly to the left hemisphere) and “different” responses were favored when presented in the LVF (transmitted direction to the right hemisphere). This gradually reversed over sessions with “same” responses becoming faster for letters presented in the LVF, and “different” responses becoming faster for stimuli presented in the RVF. The laterality acquired under these conditions was cumulative and reproducible, appeared in all 16 subjects, and was preserved between sessions a week apart. The data suggest that laterality is a flexible and reversible characteristic of the human brain even when stimulus and task remain constant.

Construct accessibility and depression: an examination of cognitive and affective factors.

Two studies in which the parameters of construct accessibility in depression were examined are reported. In Experiment 1, depressed and nondepressed subjects were required to name the colors of tachistiscopically presented depressed-content, neutral-content, and manic-content words. Because of the predicted accessibility and interference effects of the depressed-content words, the depressed subjects were expected to demonstrate longer response latencies to these words than to the non-depressed-content words. This response pattern was found for the depressed subjects; the nondepressed subjects did not demonstrate differential response latencies. In Experiment 2, a mood-induction paradigm was used to investigate whether the interference effects obtained in Experiment 1 were due to temporary mood differences between the depressed and nondepressed subjects, or were a function of more stable depression-associated patterns of information processing. Although predicted group differences were obtained on a mood adjective checklist, no effects were found for task performance. These results suggest that transient mood is not a sufficient explanation for the results obtained in Experiment 1. The implications of the present findings for the understanding of both construct accessibility and depression are discussed, and directions for future research are suggested.

Development of taste responses in rat nucleus of solitary tract.

Extracellular responses from neurons in the nucleus of the solitary tract (NST) were studied in rats aged 5 days to adulthood during chemical stimulation of the tongue with monochloride salts, citric and hydrochloric acids, sucrose, sodium saccharin, and quinine hydrochloride. Multiunit taste responses were recorded in rats at 5-7 days of age and single-unit responses were recorded from 111 neurons in four other age groups of 14-20 days, 25-35 days, 50-60 days, and adult. NST neurons in rats aged 5-7 days consistently responded to relatively high concentrations (0.5 M) of NH4Cl and KCl and to citric and hydrochloric acid. However, they often did not respond to 0.5 M NaCl or to 0.1 M NH4Cl. Single NST neurons in rats aged 14 days and older characteristically responded to all 0.1 and 0.5 M salts and to both acids. At least 75% of neurons also responded to sucrose and sodium saccharin, and 46% responded to all of these stimuli and quinine hydrochloride. After 14 days, no developmental changes occurred in the number of stimuli to which neurons responded. There were substantial developmental alterations in the response magnitudes to some chemical stimuli. Average response frequencies increased after 35 days of age for 0.1 and 0.5 M NaCl, LiCl, KCl, and for sucrose and sodium saccharin. Response frequencies for NH4Cl, citric and hydrochloric acid, and quinine hydrochloride, however, did not change throughout development. The proportion of single NST neurons that responded maximally to specific monochloride salts did not change during development. Most single neurons in all age groups responded equally well to NH4Cl, NaCl, and LiCl. No NST neuron responded maximally to KCl. There were also no developmental differences in response latencies in rats aged 14 days and older. Response frequencies of second-order NST neurons generally reflect changes in responses from the primary afferent, chorda tympani fibers, throughout development; however, the increases in salt response frequencies from NST neurons occur comparatively later in development. Furthermore, at all ages, the taste responses to monochloride salts include higher response frequencies and a general loss in response specificity in NST compared to chorda tympani neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Septal lesions and active avoidance performance in rats: Effects of differential intrabox cues

In two separate experiments, male rats received septal lesions and were compared to operated controls on the acquisition of a two-way active avoidance task. In both experiments, an automated active avoidance apparatus (Lafayette Instrument Co.) was used, and the animals were tested 10 trials each day, 6 days/week. The CS was a tone, and the US was a 0.7 mA shock; the CS-US interval was 7 seconds. In Experiment 1, the rats (N=6/group) were tested under conventional conditions. The two compartments of the avoidance apparatus were identical in all respects. In Experiment 2, the rats (N=6/group) were tested in the same apparatus, but with differential intrabox cues. The inside of the left compartment was lined with black contact paper, while the inside of the right compartment was lined with white contact paper. Irrespective of the conditions, the septal rats were facilitated in the acquisition of shuttle-avoidance. In both tasks, the septal subjects required fewer trials to reach criterion, and showed better orientation in the shuttle-box compared to controls. The response latencies of the septal subjects also tended to be faster, but neither septal nor control subjects showed differential response latencies related to the direction of the shuttle response. Previous findings have shown that the addition of external cues to purported spatial tasks can reduce the behavioral effects produced by damage to the septohippocampal axis on such tasks. The present results suggest that such a cue-addition procedure does not influence the behavioral effects produced by septal lesions in shuttle-avoidance.

Effects of practice on speeded classification of natural and synthetic speech

At the last meeting of the Society in Miami, one of us (Pisoni) presented results from a speeded classification task demonstrating increased processing time for recognition of synthetic speech. In a lexical decision task, we showed an overall increase in response time of 145 ms for synthetically produced words and nonwords over naturally produced control items. Moreover, there was no interaction between signal type and classification response suggesting that the observed differences were due to early stages of perceptual analysis in which the segmental representation is developed from the acoustic‐phonetic input. In the present investigation, we were interested in determining whether the observed differences in processing time between natural and synthetic speech could be attenuated or possibly eliminated by practice with the experimental materials and task over several days. We ran ten undergraduate subjects for five days in the lexical decision task. As expected, accuracy improved and latency decreased over the test sessions. However, the relative differences in response latency between natural and synthetic items remained roughly constant. Thus, the earlier differences observed in this speeded classification task are not due to short‐term familiarity effects. Rather they seem to reflect real differences in the perceptual and cognitive processes used to extract segmental information from the speech signal. [Supported by a research grant from NINCDS to Indiana University.]

Visual information coding in the frog optic tectum

The possible mechanisms of visual information coding in the frog optic tectum were studied by extracellular recording of unit activity. It was postulated that information is coded spatially and that its precision is increased by the use of various types of time codes, making wide use in particular of differences in response latencies. These differences are also important on their own account, and they act as a component of the time codes (latency-frequency, latency-structural, and so on). The uniform distribution of neurons processing visual information and, in particular, analyzing the different parameters of visual signals (direction-velocity, lightness-darkness, and so on), among the structures of the tectum is evidence that the mechanism of analysis of the parameters of visual stimulus movement is distributive in type.

Orienting, habituation, sensitisation, and dishabituation in the electrodermal system of consecutive, drug free, admissions for schizophrenia

Thirty-three consecutive admissions for schizophrenia with PSE diagnoses and free of neuroleptics were compared with 31 hospital staff for distinguishing features of bilateral electrodermal activity to a sequence of mild tones followed by a sequence of conspicuous tones with variation of temporal parameters. To mild tones most patients were either non-responders or non-habituators whereas most controls were habituators or non-habituators. To conspicuous tones patients as a group were more responsive but without the features of sensitisation to a test stimulus shown by controls. Patients as a group had more non-specific responses and higher levels of skin conductance which showed less adaptation than controls. To a large extent previously reported difference in response latencies, rise-times and half-recovery times would appear to be a function of habituation rate. Patient-control differences may reflect anxiety and stress in patients, though lateral asymmetries in activity have a deeper salience for the nature of schizophrenia.

The Performance of Hyperactive and Normal Boys Under Differing Reward and Punishment Schedules

Hyperactive and normal control boys were administered a discrimination learning task under feedback conditions of reward (winning marbles for correct responses) and punishment (losing marbles for incorrect responses) with continuous and partial schedules. In general, both groups of children learned more quickly under conditions of punishment than under conditions of reward and under continuous rather than partial feedback schedules. The differential effect of reward and punishment on learning was greater for the younger hyperactive boys (mean age = 9.0 years), whereas the older hyperactive (mean age = 10.6 years) and normal control group boys were not as sensitive to these feedback effects. Although all boys showed greater resistance to extinction after the punishmment condition, the hyper¯actives did not perform as well as normal boys during extinction. Hyperactive boys did not exhibit differences in response latencies from normal boys, but they did demonstrate a trend for greater variability in latency under conditions of reward. Other differences between hyperactive and normal control group boys were predicted, but they were not demonstrated in this study.

Optic nerve innervation of so-called interneurons of the rat lateral geniculate body.

In urethane-anesthetized rats, neurons responding to electrical stimulation of the optic nerve (ON) with bursts of spikes were searched for in the region of the thalamic reticular nucleus close to the dorsal nucleus of the lateral geniculate body (LGBd). These neurons were identical with those which had been presumed to be inhibitory internerons (I-cells) of LGBd. Conduction velocityes of ON fibers innervating I-cells were determined by measuring differences in response latency between stimulations of two separate sites along the contralateral ON. The velocity ranged from 1.9 to 7.3 m/sec with an average of 4.6 m/sec, indicating that among the three groups of ON fibers with different velocities, only the slowest group is involved in activation of I-Cells. Calculation of synaptic delays revealed that one group of I-cells was excited monosynaptically and another, disynaptically. Experiments on rats with the visual cortex chronically ablated provided evidence that the disynaptically excited I-cells received ON impulses via axon collaterals of principal cells of LGBd. The region of the thalamic reticular nucleus containing I-cells was found to receive inputs not only from the contralateral but also from ipsilateral ON.

Response latency differences in speech shadowing as an indicator of distinctive features of consonants.

The purpose of this study was to determine which articulatory features serve as important distinctive features of perception by measuring latency in speech shadowing. Fifteen subjects shadowed a recording of consonant-vowel syllables orally and by means of a hand-held switch. Vocal shadowing was tape recorded and the onsets of the stimuli and the manual responses were recorded on a polygraph. The oral responses were used to indicate perceptual confusions and the manual responses were used as the basis for measuring the shadowing latency for each consonant. After eliminating the dental fricatives because of perceptual confusions, the remaining consonants (p, b, t, d, k, g, f, v, s, z, ∫, 3, m, n, 1, r, j, w,) were classified according to a feature system and the latency scores were analysed. An analysis of variance indicated significant differences among sounds arranged according to features. A post hoc comparison between all possible features (interrupted, grave, acute, diffuse, strident, voiced, tense, nasal) showed that three features were primarily responsible for the significant variance: stridency (or, minus interrupted) voicing, and nasalization. The results do not seem to support the concept of a hierarchy of features which order the decisions made in consonant identification.

A right hemisphere basis for calculation in the human brain

Ss were asked to perform calculations with two-digit numbers presented by a divided visual-field technique to either the right or left hemisphere of the brain and to match the results with further numbers, responding bimanually. There was no interhemispheric difference in response latency, but analysis of errors showed that more errors were associated with presentation to the left hemisphere for subtraction problems and for all problems taken together. This apparent right-hemisphere superiority is contrasted with traditional views.

Effects of visual deafferentation on mesencephalic reticular activity in freely behaving cats

Effects of bilateral eye enucleation on maintained and evoked unit activity in the mesencephalic reticular formation (MRF) were studied in freely behaving cats. Recording of MRF units was carried out in the same way as before total visual deafferentation. Three recording conditions were classified: resting arousal, light sleep, and deep sleep. The MRF neurons initially decreased greatly, maintained discharge rates following visual deafferentation, and trended to recover their control level 1 month after deafferentation. Visual deafferentation brought about no notable change in the discharge pattern. Phasic enhancement of unit firing in deep sleep in association with bursts of phasic waves in the central visual system was still observable after deafferentation. Discharge rate and neural responsiveness of visually deafferented MRF neurons shifted between the three states in the same fashion as observed in intact neurons, i.e., light sleep → resting arousal → deep sleep in order of increasing sensitivity. After deafferentation there was much less incidence of MRF responses with longer latency although short-latency responses were well preserved. This phenomenon subsided with a lapse of time. The difference in response latency in the three states was detectable in deafferented MRF neurons. Immediately after visual deafferentation the extent of input convergence on MRF neurons tended to decrease in comparison with controls and this reduction sustained through 1 month. Visual deafferentation did not influence the sampling rate of nonresponding units in the MRF. No uniform relation between the location of units in the MRF and their maintained discharge rates was noted after visual deafferentation.

Conduction velocity of optic nerve fibers innervating lateral geniculate body and superior colliculus in the rat

Conduction velocities of the optic nerve (ON) in the rat were measured by recording evoked unitary discharges of postsynaptic cells to stimulation of the ON at two separate sites. The velocity of ON impulses to activate a given postsynaptic cell was calculated from the distance between the two stimulating sites and the difference in response latency of the same postsynaptic cell. Recordings were made from the lateral geniculate body (LGB) and the superior colliculus (SC), both contralateral to stimulation. ON fibers innervating principal cells of the LGB (P cells of Burke and Sefton) fell into three groups (t g0, t g1 and t g2) having average velocities of 19.2, 11.9, and 5.2 m/sec, respectively. Internuncial cells (I cells) received t g2 fibers only. There were also three groups of ON fibers destined for the SC (t c0, t c1 and t c2). Their average velocities were 15.4, 9.1, and 3.7 m/sec, respectively.

Sensory modality and object-naming in aphasia.

Twenty-seven aphasics, 12 right-brain-injured, and 12 normal subjects were presented with 16 objects for tactile naming, 16 for auditory naming, and 16 for olfactory naming. All 48 objects were also presented for visual naming. Comparison between groups was based on the percentage difference in response latencies between naming by vision and naming by each of the other modalities. Analysis of variance showed no significant differences. The order of increasing difficulty of stimuli was the same for all groups, with aphasics showing consistently larger differences in latency than the other two groups. With few exceptions, the aphasics' naming scores were less than 1 SD unit apart in all modalities. It was concluded that a modality nonspecific process intervenes between stimulus presentation and naming.

RESPONSE LATENCY WITH CONSTANT AND VARIABLE INTERVAL SCHEDULES.

12 independent groups were used to examine the relationship between response latency and regularity of signal occurrence. In each of 6 groups 20 simple visual signals were presented sequentially at one of 6 constant intervals. Interval durations were 10, 20, 40, 80, 160, or 320 sec. For each constant-interval group tested, there was also a variable-interval group with intervals of the same average duration. For all intervals except one (40 sec.), the variable-interval groups had longer response latencies than the constant-interval groups, the difference in response latency between the constant- and variable-interval groups increasing as a function of the duration of the interval, up to intervals of 160 sec. For both constant- and variable-interval groups, response latency varied directly with interval duration.

Differences in response latency and response variability between high and low anxiety subjects in a flicker-fusion task.

Differences in response latency and response variability between high and low anxiety subjects in a flicker-fusion task.