Biomedical subjects

Ernst Pöppel

Publications and source records attributed to Ernst Pöppel.

10 recordsLinked to original sources

PubMed2007

Two spatially separated attention systems in the visual field: evidence from inhibition of return.

It has been demonstrated that the human visual field shows some functional inhomogeneities, in particular when the central and perifoveal regions are compared to the more peripheral regions. The present study examined this inhomogeneity by examining the effect of stimulus eccentricity on inhibition of return (IOR), a phenomenon that biases our attention towards novel locations against returning it back to previously attended locations. Eighteen subjects were examined in a visual detection task, in which a target appeared randomly following a nonpredictive spatial cue in the visual field. The eccentricities of the cues and targets were systematically manipulated from 5 degrees to 30 degrees with 5 degrees increments. Results showed that response times to targets that appeared at cued locations were significantly slower than those at uncued locations for all stimulus eccentricities, demonstrating the IOR effects. However, response times at cued locations increased significantly when stimulus eccentricity shifted from 15 degrees to 20 degrees, leading to a much stronger IOR effect at more peripheral regions compared to central and perifoveal regions, indicating a functional dissociation between these two regions of the visual field. Possible neural mechanisms underlying this dissociation are discussed, and two attention systems modulating the two functional regions of the visual field are put forward to best account the present finding implicating in particular midbrain mechanism.

Attention↗

PubMed2006

A hierarchical model of operational anticipation windows in driving an automobile.

Driving an automobile is an example of a goal-directed activity with high complexity in which different behavioral elements have to be integrated and brought into a sequential order. On the basis of the reafference principle and experimental results on temporal perception and cognitive control, we propose a hierarchical model of driving behavior, which can also be adapted to other goal-directed activities. Driving is conceived of as being controlled by anticipatory neuronal programs; if these programs are disrupted by unpredictable stimuli, which require an instantaneous reaction, behavioral control returns after completion of the reactive mode to the anticipatory mode of driving. In the model different levels of anticipation windows are distinguished which, however, are interconnected, in a bi-directional way: (a) Strategic level with a representation of the driving activity from the beginning to reaching the final goal; (b) Segmented tactical level with the sequence of necessary milestones to reach the goal; (c) Maneuver level where actions like passing another car or keeping a lane are controlled; (d) Short-term integration level of a few seconds which allows immediate anticipations; and (e) Synchronization level for sensorimotor control and complexity reduction within neuronal assemblies. A flow diagram schematically describes different driving situations stressing the anticipatory mode of control. In a pilot experiment with 20 subjects using a virtual driving situation in a car simulator predictions of the model could be verified, i.e., subjects showed a significant preference for the anticipatory mode of driving.

Automobile Driving↗

PubMed2005

Effects of display position of a visual in-vehicle task on simulated driving.

To determine the relative safety of onboard display positions while driving, participants performed a lane-keeping task in a driving simulator. Concurrently, they reacted to a light by pushing the brake pedal. A secondary task was projected onto a display at one of the seven different locations in the cockpit. Behavioral data, eye movements, and subjective rating scales showed that the manipulation of display information during driving disturbed drivers' performance exponentially as a function of distance between the line of sight to the outside primary task and the onboard display position. Vertical eccentricity had a greater detrimental effect than horizontal distance. Under a certain condition with a high secondary task load, reaction time of pushing the brake to the outside stimulus nearly doubled with a diagonal eccentricity of 35 degrees as compared to lower eccentricities. Subjective workload measures complement the behavioral data of clear detrimental effects with eccentricities of at least 35 degrees .

Automobile Driving↗

PubMed2004

Three bands of oscillatory activity in the lateral geniculate nucleus of the cat visual system.

Neuronal responses in the cat lateral geniculate nucleus were analyzed with respect to oscillatory components in 5930 peri-stimulus time histograms recorded in 69 neurons. Oscillatory components were observed in three frequency ranges clearly separated from each other, i.e. in a lower range between 25 and 33 Hz (mean 27.8 Hz), in a middle range between 45 and 60 Hz (mean 52.5 Hz), and in a higher range between 75 and 100 Hz (mean 84.4 Hz); temporal variance within the neuronal populations showing oscillatory characteristics increased with higher frequencies. Although the frequency ranges of the oscillatory responses were clearly separated from each other, a functional dependence between these three populations of geniculate neurons appears to be possible; the numerical relationship of approximately 1:2:3 points to the possibility of a temporal coupling between distinct neuronal populations at an early stage of visual processing.

Action Potentials↗

PubMed2004

Temporal processing deficits in high-functioning children with autism.

It is well known that complex functions (e.g. perception, attention, memory, emotions, social interactions and language) are usually disturbed in autism. As these functions are characterized by specific temporal patterns, the present study examined whether children with autism show typical temporal processing in the time domain of a few seconds. Using a temporal-reproduction paradigm, we found that they were unable to link their responses to stimulus duration. Independently of stimulus duration, they reproduced auditory or visual stimuli with the same response duration of, on average, 3 s. These results demonstrate important deficits in duration judgment in individuals with autism. As other experiments provide evidence for a temporal processing platform of approximately 2-3 s in normal individuals, this platform may be preserved in a residual form in autism.

Adolescent↗

PubMed2004

Lost in time: a historical frame, elementary processing units and the 3-second window.

The main topics of time and timing in psychology, cognitive neuroscience and biology have been formulated already in the nineteenth century. Unfortunately, time and timing as a challenging topic has been put to rest for quite some time, but has become a central issue again during the last years. It has become clear, that perceptual or cognitive processes can only be understood if the dimension of time is taken more seriously. The reduction of complexity in neuronal systems is for instance, achieved by temporal integration mechanisms which are independent of the content of a percept or a cognitive act but are presemantical operations. It is essential to distinguish between content functions and logistical functions that provide presemantically defined temporal frames for mental activity.

History, 19th Century↗

PubMed2004

Two types of anticipation in synchronization tapping.

The time perception mechanism in anticipatory timing control was investigated in a synchronization tapping task. An especially negative asynchrony phenomenon in which the tap onset precedes the stimulus onset was used as an anticipatory response. In this experiment, to clarify the effects of higher brain functions, such as attention, a dual-task method was applied and a word memory task was used as a secondary task. The results revealed two types of anticipatory mechanisms from the standpoint of attentional resources involved in time perception. One is the anticipatory tapping that is influenced by attention and seen in the interstimulus-onset interval (ISI) range of 1,800 to 3,600 ms. In this region, the magnitude of synchronization error (SE) between tap onset and stimulus onset was scaled by the ISI. The other is the automatic anticipation that is not affected by attention and is seen in the 450 to 1,500 ms range. SE in this region was constant and independent of the ISI. Accordingly, this anticipatory timing mechanism in synchronous tapping is thought to be a dual process including the attention processing of temporal information and the embodied automatic anticipation.

Adult↗

PubMed2002

Duration processing in children as determined by time reproduction: implications for a few seconds temporal window.

From research carried out over recent years using different experimental paradigms, it has become apparent that central information processing is temporally segmented into sequential units of a few seconds. This segmentation presumably reflects a neuronal process of temporal integration (TI) which automatically binds successive events into temporal units. Support for such TI comes, for example, from studies on temporal reproduction where standards up to approximately 2-3 s are reproduced veridically. Using this paradigm of temporal reproduction, we investigated the effect of normal cognitive development of sensory modality and of the range of presented standards on TI. Sixty children aged 6-7, 9-10 and 13-14 years reproduced visual or auditory standard durations ranged from 1 to 5.5 s or from 1 to 3 s. The results showed that durations of approximately 2 s were reproduced correctly, whereas those longer than 2.5 s were under-reproduced in the three age groups. For standards shorter than 2 s substantial age-related differences were revealed: the youngest group displayed significant over-reproduction comparing to older subjects. These observations indicate that the upper limit for TI is a stable feature across the different age groups. Furthermore an age-related modulation within the temporal window of the operating TI seems to be linked to cognitive development.

Adolescent↗

PubMed2002

Temporal order judgement for auditory and visual stimuli.

The ability to perceive temporal order for pairs of auditory and visual stimuli was investigated in 12 volunteers. They were asked to make judgements about the order of presented stimuli by pressing two response buttons in a certain order. The performance on auditory and visual tests was studied in relation to the Inter-Stimulus-Interval (ISI), which varied from 5 to 500 ms. In general, the level of performance was similar for the two modalities and the criterion of 75% of correct responses was reached at ISI longer than 40 ms, independently of the modality. These findings are consistent with previous research. However, at ISI of 5 ms, a significantly higher level of correctness was observed for the auditory than visual task. Such a tendency was also observed for ISIs of 10, 20 and 40 ms. Better processing in the auditory compared to the visual task at shorter ISIs may result from a different kind of transduction mechanism at the level of receptive cells in each modality. Alternatively, subjects may use two different kinds of response strategies in the auditory modality, only one being comparable to the response strategy in the visual modality.

Acoustic Stimulation↗

PubMedDate not supplied

Effects of Ginkgo biloba on mental functioning in healthy volunteers.

BACKGROUND: There has been a lack of investigations examining the effects of Ginkgo biloba extract EGb 761 on mental functions and quality of life in healthy subjects with no cognitive impairment. Thus, the objective of the present study was to evaluate the relatively short-term (i.e., 4 weeks) effects of EGb 761 on mental functioning and quality of life in healthy volunteers. METHODS: The trial was conducted as a 4-week, randomized, double-blind, placebo-controlled, parallel-group, monocentric study. Sixty six healthy volunteers aged between 50 and 65 years without age-associated cognitive impairment were randomized, 32 into the placebo and 34 into the EGb 761-treatment group (240 mg, t.i.d.). Safety and compliance were monitored after 1, 2, 3 and 4 weeks. Primary outcome measures in this study are the subjects' judgment of their own mental health (MH), their general health (GH) and their quality of life (QoL) operationalized on the basis of three different visual analog scales (VAS). Secondary outcome measures are 15 tests and experimental procedures based on a neurobiologically based classification or taxonomy of functions. RESULTS: Intergroup differences in self-estimated mental health as well as self-estimated quality of life were significant in favor of EGb 761. No intergroup differences were found in self-estimated general health. Secondary outcomes supporting the notion of superiority of the active drug were found for both motor performance and emotional evaluation. This study did not reveal evidence of unknown drug-induced side effects or intolerance. No serious adverse events were observed during the study. CONCLUSIONS: Both questions treated in this study, efficacy and safety, are important from a medical perspective because many persons take the agent studied in an effort to enhance their mental functioning and general well-being. The findings of this study support the adequacy of intake of EGb 761 to improve the functions indicated previously.

Aged↗