Hemispheric differences in normal human subjects: further evidence from study of reaction time to lateralized visual stimuli

Evidence is presented that the phylogenetically older retin-otectal pathway contributes to reflex orienting of visual attention in normal human subjects. The study exploited a lateralized neuroanatomic arrangement of retinotectal pathways that distinguishes them from those of the geniculostriate system; namely, more direct projections to the colliculus from the temporal hemifield. Subjects were tested under monocular viewing conditions and responded to the detection of a peripheral signal by making either a saccade to it or a choice reaction time manual keypress. Attention was summoned by noninformative peripheral precues, and the benefits and costs of attention were calculated relative to a central precue condition. Both the benefits and costs of orienting attention were greater when attention was summoned by signals in the temporal hemifield. This temporal hemifield advantage was present for both saccade and manual responses. These findings converge with observations in patients with occipital and midbrain lesions to show that the phylogenetically older retinotectal pathway retains an important role in controlling visually guided behavior; and they demonstrate the usefulness of temporal-nasal hemifield asymmetries as a marker for investigating extrageniculate vision in humans.

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Auditory Influences on Visual Temporal Rate Perception

Journal of Neurophysiology ◽

10.1152/jn.00706.2002 ◽

2003 ◽

Vol 89 (2) ◽

pp. 1078-1093 ◽

Cited By ~ 143

Author(s):

Gregg H. Recanzone

Keyword(s):

Visual Perception ◽

Auditory System ◽

Human Subjects ◽

Visual Stimuli ◽

Sensory System ◽

Spatial Location ◽

Auditory Stimuli ◽

Spatial Tasks ◽

Normal Human ◽

Temporal Rate

Visual stimuli are known to influence the perception of auditory stimuli in spatial tasks, giving rise to the ventriloquism effect. These influences can persist in the absence of visual input following a period of exposure to spatially disparate auditory and visual stimuli, a phenomenon termed the ventriloquism aftereffect. It has been speculated that the visual dominance over audition in spatial tasks is due to the superior spatial acuity of vision compared with audition. If that is the case, then the auditory system should dominate visual perception in a manner analogous to the ventriloquism effect and aftereffect if one uses a task in which the auditory system has superior acuity. To test this prediction, the interactions of visual and auditory stimuli were measured in a temporally based task in normal human subjects. The results show that the auditory system has a pronounced influence on visual temporal rate perception. This influence was independent of the spatial location, spectral bandwidth, and intensity of the auditory stimulus. The influence was, however, strongly dependent on the disparity in temporal rate between the two stimulus modalities. Further, aftereffects were observed following approximately 20 min of exposure to temporally disparate auditory and visual stimuli. These results show that the auditory system can strongly influence visual perception and are consistent with the idea that bimodal sensory conflicts are dominated by the sensory system with the greater acuity for the stimulus parameter being discriminated.

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Simple and choice reaction times to lateralized visual stimuli in normal human subjects

Brain Research ◽

10.1016/0006-8993(70)90224-6 ◽

1970 ◽

Vol 24 (3) ◽

pp. 557-558 ◽

Cited By ~ 1

Keyword(s):

Human Subjects ◽

Visual Stimuli ◽

Reaction Times ◽

Normal Human ◽

Choice Reaction Times

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Triggering of preprogrammed movements as reactions to masked stimuli

Journal of Neurophysiology ◽

10.1152/jn.1990.63.3.439 ◽

1990 ◽

Vol 63 (3) ◽

pp. 439-446 ◽

Cited By ~ 122

Author(s):

J. L. Taylor ◽

D. I. McCloskey

Keyword(s):

Human Subjects ◽

Visual Stimuli ◽

Backward Masking ◽

Motor Reaction ◽

Large Stimulus ◽

Motor Responses ◽

Small Stimulus ◽

Complex Motor ◽

Normal Human ◽

Choice Testing

1. Visual stimuli were presented to normal human subjects to test simple and more complex voluntary motor responses. Large and small visual stimuli were presented. In some trials, the small stimulus was followed 50 ms later by the large stimulus, so that the small stimulus was not perceived; this is the phenomenon of "backward masking." 2. Although subjects were not able to detect the masked, visual stimulus on forced-choice testing, they performed motor, reaction-time (RT) tasks in response to it. The RTs for responses to the masked stimulus were the same as those for responses to the easily perceived, nonmasked stimulus. 3. This result confirms and extends the findings of Fehrer and Biederman and was demonstrated with both simple and more complex motor responses. 4. Discussion of the findings focuses on their implications for motor control, particularly with respect to the preprogramming of voluntary movement.

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Observations on a Relationship between Steroid Metabolism and the Concentration of Plasma Fibrinogen

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654793 ◽

1963 ◽

Vol 10 (02) ◽

pp. 400-405 ◽

Cited By ~ 4

Author(s):

B. A Amundson ◽

L. O Pilgeram

Keyword(s):

Blood Coagulation ◽

Methyl Ether ◽

Broad Spectrum ◽

Human Subjects ◽

Plasma Fibrinogen ◽

Steroid Metabolism ◽

Specific Site ◽

Chain Reaction ◽

Normal Human ◽

A Chain

SummaryEnovid (5 mg norethynodrel and 0.075 mg ethynylestradiol-3-methyl ether) therapy in young normal human subjects causes an increase in plasma fibrinogen of 32.4% (P >C 0.001). Consideration of this effect together with other effects of Enovid on the activity of specific blood coagulatory factors suggests that the steroids are exerting their effect at a specific site of the blood coagulation and/or fibrinolytic system. The broad spectrum of changes which are induced by the steroids may be attributed to a combination of a chain reaction and feed-back control.

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Relationship Between Mepacrine-Labelled Dense Body Number, Platelet Capacity to Accumulate 14C-5-HT and Platelet Density in the Bernard-Soulier and Hermansky-Pudlak Syndromes

Thrombosis and Haemostasis ◽

10.1055/s-0038-1666908 ◽

1979 ◽

Vol 42 (02) ◽

pp. 694-704 ◽

Cited By ~ 31

Author(s):

F Rendu ◽

A T Nurden ◽

M Lebret ◽

J P Caen

Keyword(s):

Dense Body ◽

Human Subjects ◽

Human Platelets ◽

Dense Bodies ◽

Storage Organelle ◽

Hereditary Disorders ◽

Labelling Procedure ◽

Normal Human ◽

Hermansky Pudlak Syndrome ◽

Bernard Soulier Syndrome

SummaryWe have used the mepacrine-labelling procedure to measure the dense body (serotonin storage organelle) content of the platelets of 2 hereditary disorders where abnormalities in dense body number were suspected. The platelets were incubated with mepacrine and examined by fluorescence microscopy. A mean number of 5.4 ± 0.8 (SD) dense bodies per platelet was calculated from the data obtained using platelets isolated from 40 normal human subjects. In contrast the platelets of 2 patients with the Bernard-Soulier syndrome contained an average of 14 and 17 labelled granules. This increase was associated with a much greater capacity of the platelets to accumulate 14C-5-HT. The opposite result was obtained using the platelets from 2 patients with the Hermansky-Pudlak syndrome which contained few granules labelled by mepacrine and took up less 14C-5-HT than normal human platelets. Centrifugation of the patients’ platelets on discontinuous sucrose gradients showed that the platelets of the 2 Bemard-Soulier patients were much denser than normal whereas a high proportion of low density platelets was observed in the Hermansky-Pudlak syndrome. These results further define the platelet abnormalities in the two syndromes and suggest that dense body number may be one of the factors governing platelet density.

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ADRENERGIC CONTROL MECHANISM FOR ACTH SECRETION IN MAN

Acta Endocrinologica ◽

10.1530/acta.0.0740263 ◽

1973 ◽

Vol 74 (2) ◽

pp. 263-270 ◽

Cited By ~ 50

Author(s):

Yoshikatsu Nakai ◽

Hiroo Imura ◽

Teruya Yoshimi ◽

Shigeru Matsukura

Keyword(s):

Intravenous Infusion ◽

Human Subjects ◽

Blocking Agent ◽

Inhibitory Effect ◽

Plasma Acth ◽

Acth Secretion ◽

Glucose Levels ◽

Alpha Receptors ◽

Normal Human ◽

Adrenergic Blocking

ABSTRACT In order to determine if an adrenergic mechanism is involved in the secretion of corticotrophin (ACTH), the effect of adrenergic-blocking or -stimulating agent on plasma ACTH, cortisol and glucose levels was studied in normal human subjects. The intravenous infusion of methoxamine, an alpha adrenergic-stimulating agent, caused a rise in plasma ACTH and cortisol. This increase in plasma ACTH and cortisol was significantly inhibited by the simultaneous administration of phentolamine, an alpha adrenergic-blocking agent, in combination with methoxamine. The intravenous infusion of propranolol, a beta adrenergic-blocking agent, caused no significant change in plasma ACTH and cortisol, although it enhanced the plasma ACTH response to insulin-induced hypoglycaemia. On the other hand, alpha adrenergicblockade by intravenous infusion of phentolamine significantly suppressed the plasma ACTH response to insulin-induced hypoglycaemia. These studies suggest a stimulatory effect of alpha receptors and a possible inhibitory effect of beta receptors on ACTH secretion in man.

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Specialized systems for the processing of mnemonic information within the primate frontal cortex

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1996.0130 ◽

1996 ◽

Vol 351 (1346) ◽

pp. 1455-1462 ◽

Cited By ~ 229

Keyword(s):

Frontal Cortex ◽

Specific Activity ◽

Human Subjects ◽

Long Term Memory ◽

Executive Processing ◽

Severe Impairment ◽

Normal Human ◽

Short And Long Term ◽

Cortical Association Areas

The lateral frontal cortex is involved in various aspects of executive processing within short- and long-term memory. It is argued that the different parts of the lateral frontal cortex make distinct contributions to memory that differ in terms of the level of executive processing that is carried out in interaction with posterior cortical systems. According to this hypothesis, the mid-dorsolateral frontal cortex (areas 46 and 9) is a specialized system for the monitoring and manipulation of information within working memory, whereas the mid-ventrolateral frontal cortex (areas 47/12 and 45) is involved in the active retrieval of information from the posterior cortical association areas. Data are presented which support this two-level hypothesis that posits two distinct levels of interaction of the lateral frontal cortex with posterior cortical association areas. Functional activation studies with normal human subjects have demonstrated specific activity within the mid-dorsolateral region of the frontal cortex during the performance of tasks requiring monitoring of self-generated and externally generated sequences of responses. In the monkey, lesions restricted to this region of the frontal cortex yield a severe impairment in performance of the above tasks, this impairment appearing against a background of normal performance on several basic mnemonic tasks. By contrast, a more severe impairment follows damage to the mid-ventrolateral frontal region and functional activation studies have demonstrated specific changes in activity in this region in relation to the active retrieval of information from memory.

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