Biomedical subjects

Deborah M Saucier

Publications and source records attributed to Deborah M Saucier.

At least 19 recordsLinked to original sources

PubMed2006

The influence of aging on recovery following ischemic brain damage.

Stroke is a health hazard that affects all age groups, however the impact of age on brain injury following ischemia remains largely unexamined. We examined the extent to which age, from the newborn to mature adult, affects behavioral recovery following similar degrees of ischemic brain damage. We utilized a model that produces comparable volumes of brain damage between the different ages. Endothelin-1, a potent vasoconstrictor, was injected into the brain of 10, 63 and 180-day-old rats, at the level of the right middle cerebral artery. On days 3, 7, 14, 28 and 56 post-insult, behavioral tests including rota-rod, foot-fault, open-field, inclined screen, tape-removal test and postural reflex were performed. Control animals underwent sham surgery, but ischemia was not induced. Neuropathology was assessed on day 63 post-insult. Volume of damage was determined for each brain as a percentage of the contralateral hemisphere (which remains undamaged). Our results indicated that the volume of damage for each age group was 22.97, 19.97, and 18.85% for 10, 63 and 180-day-old rats, respectively, and were not significantly different from each other. Overall, ischemic animals did significantly more poorly on behavioral testing than did controls. When broken down by age, the difference between ischemics and controls was only evident in the 63 and 180-day-old animals. The tape-removal test revealed main effects of age, group, and day (p<0.001). In addition, significant interactions were noted for day of testing by age (p<0.001), day of testing by group with ischemics performing more slowly than controls, and an age by group interaction which indicated that the 63 and 180-day-old ischemic rats did not recover completely during the testing period and remained significantly slower than their controls (p<0.001). In the foot-fault task, the 63 and 180-day-old ischemic animals performed significantly more poorly on days 3, 7, and 14 of recovery, returning to control values by day 28. The 180-day olds performed more poorly on day 3 of recovery, but then returned to control values. For open-field testing, the results indicate an overall difference between ischemics and controls, with the 63 and 180-day-old animals improving with time though they did not achieve control values. In conclusion our data suggest functional performance is poorly and inconsistently correlated with the extent of morphologic injury across all age groups. The immature rat clearly recovers more completely and more rapidly than do older, more mature rats. The findings may imply a greater degree of brain plasticity in the infant rat compared to the adult, and have important implications related to the underlying mechanisms of recovery and the association between brain damage and functional improvement.

Age Factors↗

PubMed2006

When advertising turns "cheeky"!

Portraits typically exhibit leftward posing biases, with people showing more of their left cheek than their right. The current study investigated posing biases in print advertising to determine whether the product advertised affects the posing bias. As the posing bias may be decreasing over time, we also investigated changes in posing biases over a span of more than 100 years. The current investigation coded 2664 advertisements from two time periods; advertisements were coded for target group of advertisement (men, women, both) and posing bias (rightward, leftward, or central). Unlike other studies that typically observe a leftward posing bias, print advertisements exhibit a rightward posing bias, regardless of time-frame. Thus, print advertisements differ greatly from portraits, which may relate to the purpose of advertisements and the role of attractiveness in advertising.

Advertising↗

PubMed2006

Photographer preference or image purpose? An investigation of posing bias in mammalian and non-mammalian species.

Portraits of human adults typically exhibit leftward biases--that is, they depict individuals with their left cheek prominently featured. The purpose of this study was to determine if photographs of human infants and photographs of non-human animals also display these leftward biases. We observed significant leftward biases in photographs of infants and non-human animals. The only exception to this was a rightward bias observed for photographs of non-mammalian species that were found on personal websites. As the species sampled were likely unaware of the purpose of the photographs, our data are consistent with the interpretation that these biases reflect the preference of the photographer.

Animals↗

PubMed2005

Rightward biases in free-viewing visual bisection tasks: implications for leftward responses biases on similar tasks.

Neurologically normal individuals exhibit strong leftward response biases during free-viewing perceptual judgments of brightness, quantity, and size. When participants view two mirror-reversed objects and they are forced to choose which object appears darker, more numerous, or larger, the stimulus with the relevant feature on the left side is chosen 60-75% of the time. This effect could be influenced by inaccurate judgments of the true centre-point of the objects being compared. In order to test this possibility, 10 participants completed three visual bisection tasks on stimuli known to elicit strong leftward response biases. Participants were monitored using a remote eye-tracking device and instructed to stare at the subjective midpoint of objects presented on a computer screen. Although it was predicted that bisection errors would deviate to the left of centre (as is the case in the line bisection literature), the opposite effect was found. Significant rightward bisection errors were evident on two of the three tasks, and the leftward biases seen during forced-choice tasks could be the result of misjudgments to the right of centre on these same tasks.

Adolescent↗

PubMed2005

Protein-energy malnutrition impairs functional outcome in global ischemia.

We investigated whether protein-energy malnutrition (PEM) exacerbates brain injury in global ischemia. It was hypothesized that PEM would increase secondary brain damage by worsening ischemia-induced depletion of glutathione (GSH) and increasing oxidative stress. Adult male gerbils were fed an adequate protein (12.5%; C) or low protein (2%; PEM) diet for 4 weeks and subjected to 5 min of bilateral carotid artery occlusion (Ischemia) or sham surgery (Sham). At 12 h post-ischemia, GSH and markers of oxidative stress were measured in hippocampus and neocortex. The remaining gerbils were tested in the open field on days 3, 7, and 10, with viable hippocampal CA1 neurons assessed on day 10. Although the habituation of C-Ischemia gerbils in the open field was normal by day 7, PEM-Ischemia gerbils failed to habituate even by day 10 and spent greater time in the outer zone (P < 0.05). Mean (+/-SEM) total number of viable CA1 neurons at 10 days post-ischemia were C-Sham = 713 (13), C-Ischemia = 264 (48), PEM-Sham = 716 (12), and PEM-Ischemia = 286 (66). Although PEM did not increase CA1 neuron loss caused by ischemia, a subset (4/12) of PEM-Ischemia gerbils showed dramatic reactive gliosis accompanied by extensive neuronal loss. Hippocampal protein thiols were decreased by PEM and ischemia. Although the mechanism is yet to be established, the finding that PEM worsens functional outcome following global ischemia is clinically relevant since 16% of elderly are nutritionally compromised at the time of admission for stroke.

Animals↗

PubMed2005

Involvement of extracellular regulated kinase and p38 kinase in hippocampal seizure tolerance.

The mechanisms underlying brain seizure tolerance, a phenomenon in which brief periods of seizures protect brain against the lethal effects of subsequent sustained seizures, are poorly understood. Because brain seizure tolerance and brain ischemia tolerance likely share certain common mechanisms, the recent evidence that activation of extracellular regulated kinase (ERK) and p38 kinase pathways plays a critical role in ischemic preconditioning suggests that a similar mechanism may underlie brain seizure tolerance. We investigated the hypothesis in a rat kainic acid preparation of seizure preconditioning and tolerance, which was established by induction of one episode of priming epileptic status lasting for 20 min on the first day and another episode of sustained epileptic status lasting for 2 hr on the second day. We observed that acute seizures lead to a rapid activation of ERK and p38 in the hippocampal CA3 area, the brain region most susceptible to the lethal effects of epileptic status. Pretreatment with the ERK inhibitor PD98059 and the p38 inhibitor SB203580 selectively reduces seizure-elicited activation of ERK and p38, respectively, and significantly reduces priming seizure-induced protection of CA3 neurons. These findings indicate that, similar to brain ischemia tolerance, brain seizure tolerance also involves the ERK and p38 signaling pathways.

Animals↗

PubMed2005

Men are more accurate than women in aiming at targets in both near space and extrapersonal space.

Men excel at motor tasks requiring aiming accuracy whereas women excel at different tasks requiring fine motor skill. However, these tasks are confounded with proximity to the body, as fine motor tasks are performed proximally and aiming tasks are directed at distal targets. As such, it is not known whether the male advantage on tasks requiring aiming accuracy is because men have better aim or is better in the proximal domain in which the task is usually presented. 18 men (M age = 20.6 yr., SD = 3.0) and 20 women (M age = 18.7 yr., SD = 0.9) performed 2 tasks of extrapersonal aiming accuracy (>2 m away), 2 tasks of aiming accuracy performed in near space (< 1 m from them), and a task of fine motor skill. Men outperformed women on both the extrapersonal aiming tasks, and women outperformed men on the task of fine motor skill. However, a male advantage was observed for one of the aiming tasks performed in near space, suggesting that the male advantage for aiming accuracy does not result from proximity.

Adolescent↗

PubMed2004

Preventing hyperthermia decreases brain damage following neonatal hypoxic-ischemic seizures.

Neonatal seizures are the most common manifestation of underlying cerebral dysfunction. Hypoxic-ischemic encephalopathy is the cause of seizures in 40-60% of newborns. Previous work from our laboratory demonstrates that seizures associated with a hypoxic-ischemic insult results in aggravation of neuronal cell death, specifically within the hippocampus. The latter occurs in the setting of spontaneously occurring hyperthermia of 1.5 degrees C. The purpose of this study was to determine whether preventing the onset of seizure induced hyperthermia would be neuroprotective. Three groups of 10-day old rat pups received unilateral hypoxic-ischemic insults for 30 min followed by KA-induced seizures. Hyperthermia was prevented by lowering the environmental temperature ("relative hypothermia") to 29 degrees C such that the seizuring rat pups were normothermic. In one group, the prevention of hyperthermia occurred immediately following hypoxia-ischemia, whereas in the other group it occurred at the onset of seizures. The third group of rat pups (controls) remained at their nesting temperature and therefore became hyperthermic during seizures. Early (3 days) and late (20 days) neuropathology was assessed. Rat pups in whom hyperthermia was prevented during seizures displayed a significant reduction in brain damage compared to controls (p<0.05). Assessment of hippocampal brain damage also showed a significant improvement in neuronal necrosis at 20 days of recovery compared to 3 days of recovery (p<0.05). The results indicate that preventing spontaneous hyperthermia in this model of hypoxic-ischemic seizures in the newborn is neuroprotective.

Analysis of Variance↗

PubMed2004

Unilateral forced nostril breathing affects dichotic listening for emotional tones.

Unilateral forced nostril breathing (UFNB) through the left nostril is associated with enhanced spatial abilities, whereas UFNB through the right nostril is associated with enhanced verbal abilities. However, the effects of UFNB on standard tasks of laterality (e.g., dichotic listening) are unknown. This study employed dichotic listening for word targets, which typically exhibits a right ear advantage (REA), and dichotic listening for emotional targets, which typically exhibits a left ear advantage (LEA). Participants were asked to breathe either through their dominant nostril (congruent UFNB) or to breathe through their non-dominant nostril (incongruent UFNB) for the entire testing session. There was a significant three-way interaction between the type of dichotic listening task, nostril dominance, and nostril assignment, with the expected REA for word targets and the expected LEA for emotional targets-with one exception. Right nostril dominant participants assigned to the congruent condition exhibited an LEA for emotional targets (p < .05). The other three groups exhibited the expected LEA/right hemisphere advantage for the detection of emotional targets and all groups exhibited the expected REA/left hemisphere advantage for detection of word targets. As such, possible bias induced by tactile stimulation of the contralateral face cannot account for these results. Thus, our data are consistent with a selective enhancement of right hemispheric lateralized functions by right nostril UFNB.

Acoustic Stimulation↗

PubMed2004

Selective antiepileptic effects of N-palmitoylethanolamide, a putative endocannabinoid.

PURPOSE: The purpose of this study was to determine whether N-palmitoylethanolamide (PEA), a putative endocannabinoid, would be effective against kindled amygdaloid seizures. For a comparison with earlier work, we also tested the effectiveness of PEA against pentylenetetrazol (PTZ)-induced convulsions. METHODS: Kindling electrodes were implanted bilaterally in the amygdala in 32 Long-Evans rats. After the kindling of generalized (stage 5) seizures, the effects of PEA administration [i.p.; 1, 10, 100 mg/kg in dimethylsulfoxide (DMSO)] were evaluated for anticonvulsant activity. PEA (40 mg/kg, i.p. in DMSO) also was tested for anticonvulsant activity against PTZ-induced convulsions (75 mg/kg, i.p.). RESULTS: After i.p. administration of PEA, kindled rats displayed an increased latency to clonus at the 1-mg/kg dose. No other dose-dependent effects were noted. When tested against PTZ-induced convulsions, PEA protected against tonic convulsions and prolonged the latency between convulsive episodes. CONCLUSIONS: PEA produces antiepileptic effects, but does not completely suppress seizures. The mechanism of action of PEA remains to be defined.

Amides↗

PubMed2004

Throwing accuracy during prism adaptation: male advantage for throwing accuracy is independent of prism adaptation rate.

Previous studies have found that men are more accurate at throwing an object at a target than are women, independent of experience. However, these studies' results are based on average scores from multiple trials. As such, it is unknown whether the male advantage results from superior throwing accuracy or from a superior ability to calibrate subsequent throws. This study examined whether men can calibrate repeated throws more quickly and accurately than women, 25 men and 30 women were required to throw velcro-covered balls at a carpet-covered target, both with and without 10-diopter prism lenses. Participants had multiple trials in both conditions. Analyses examined whether there was a sex difference in the rate of adaptation to the prism lenses (as indicated by calibration of subsequent throws), instead of simply averaging all throwing accuracy scores and looking for an overall sex difference. Men threw the balls significantly more accurately than women, both with and without the prism lenses. However, there was no significant sex difference found on the rate of prism adaptation, as measured by improvement across the trials, i.e., calibration. Although men were more accurate at throwing balls overall, there was no sex difference in calibration of subsequent throws in adapting to the prism lenses, therefore indicating that the male advantage in throwing accuracy does not result from superior ability to calibrate subsequent throws but rather from superior throwing accuracy overall.

Accommodation, Ocular↗

PubMed2003

Right-hemispheric dominance for processing extended non-linguistic frequency transitions.

The left hemisphere is specialized for most linguistic tasks and the right hemisphere is specialized for many non-linguistic tasks, but the cause of these functional asymmetries is unknown. One of the stimulus factors that appears to influence these asymmetries is the rate at which stimuli change. In the present experiment, 41 participants completed the Fused Dichotic Words Test (FDWT) and a non-linguistic Frequency Transition Task (FTT) wherein the Frequency Transitions (FTs) were either rapid (40 ms) or relatively slow (200 ms). There was a right hemisphere advantage for slow FTs when the change was at the front of the stimulus, but no corresponding left hemisphere advantage for the rapid FTs. There was no relationship between either FTT and the left hemisphere advantage exhibited on the FDWT. This finding provides support for the position that the right hemisphere dominates tasks that require temporal processing over relatively long periods of time.

Adult↗

PubMed2003

Dissociating semantic and perceptual components of synaesthesia: behavioural and functional neuroanatomical investigations.

Colour digit synaesthetes experience atypical dual perceptions wherein achromatic digits are perceived along with coloured photisms. Recent studies have employed Stroop or priming tasks and exhibited interference or facilitation in synaesthesia [Nature 410 (2001) 580-582; Perception 28 (1999) 651-664]. We compared a synaesthete to a semantic control with arbitrary colour-number associations and demonstrated that these tasks do not elicit effects unique to synaesthesia. In contrast, we present functional neuroimaging data that clearly differentiates between these two conditions.

Acoustic Stimulation↗

PubMed2003

Female advantage in speeded colour naming: a special naming factor or superior motor sequencing?

Women name colours more quickly than men do, and our recent research suggests that the female advantage for colour naming extends to speeded naming of shapes. The female advantage could reflect a superiority in producing and execuring the motor sequences underlying the required vocal response. Or, women could have faster access to or retrieval of colour labels. The present study tested these two possibilities by administering 3 speeded colour-naming tasks. In the first task, participants named a patch of colour as quickly as possible after it was presented. In the second task, participants made manual (instead of vocal) responses. In the third task, vocal responses were required but a randomly varying delay period was introduced between the presentation of the colour patch and the required response. Females reponded more quickly on the first task but there was no such advantage in the manual or delayed conditions. Taken together, these results suggest that the female advantage for speeded naming tasks reflects an advantage for sequencing movements rather than a special naming ability.

Adult↗

PubMed2003

A Mozart effect for women on a mental rotations task.

During the past decade, there have been numerous reports of a brief, but statistically significant, improvement in immediate spatial-temporal performance after listening to 10 min. of Mozart's Sonata K.448, known as the "Mozart effect." The purpose of the present study was to assess whether production of the effect is influenced by length of listening conditions or sex. Each of 52 right-handed participants (26 females, 26 males) completed a paper-folding and cutting task and a Mental Rotations task following a listening condition in which the Mozart sonata was played and a silent condition (no music was played). A significant 3-way interaction among sex, listening condition, and task indicated that an effect was present only for women on the Mental Rotations task. As such, researchers should investigate the role of sex in production of the Mozart effect.

Adult↗

PubMed2002

Relations between brain pathology and temporal lobe epilepsy.

Temporal lobe epilepsy, the most common type of epilepsy in adult humans, is characterized clinically by the progressive development of spontaneous recurrent seizures of temporal lobe origin and pathologically by hippocampal neuronal loss and mossy fiber sprouting. In this study, we sought to test the prominent hypothesis that neuronal loss and mossy fiber sprouting play a critical role in the genesis and progression of temporal lobe epilepsy. Rats receiving a single kainic acid injection experienced a single sustained episode of epileptic status with massive neuronal loss and mossy fiber sprouting, whereas rats receiving triple kainic acid injections experienced two priming episodes and one sustained episode of epileptic status with no detectable neuronal loss and mossy fiber sprouting. Early in the process of chronic seizure development, primed rats that failed to show detectable neuronal loss and mossy fiber sprouting exhibited a starting date and a frequency of spontaneous recurrent seizures similar to those of nonprimed rats that showed massive neuronal loss and mossy fiber sprouting. However, nonprimed rats displayed significantly prolonged episodes of spontaneous recurrent seizures over the whole process of chronic seizure development and more frequent severe seizures later in the process. Similar results were observed in both Fischer-344 and Wistar rats as well as in the rat pilocarpine preparation of temporal lobe epilepsy. These results fail to reveal a relation between neuronal loss-mossy fiber sprouting and the genesis of temporal lobe epilepsy but suggest that neuronal loss, mossy fiber sprouting, or both contribute to the intensification of chronic seizures.

Animals↗

PubMed2002

Are sex differences in navigation caused by sexually dimorphic strategies or by differences in the ability to use the strategies?

When navigating, women typically focus on landmarks within the environment, whereas men tend to focus on the Euclidean properties of the environment. However, it is unclear whether these observed differences in navigational skill result from disparate strategies or disparate ability. To remove this confound, the present study required participants to follow either landmark- or Euclidean-based instructions during a navigation task (either in the real-world or on paper). Men performed best when using Euclidean information, whereas women performed best when using landmark information, suggesting a dimorphic capacity to use these 2 types of spatial information. Further, a significant correlation was observed between the mental rotation task and the ability to use Euclidean information, but not the ability to use landmark information.

Analysis of Variance↗

PubMedDate not supplied

A new model for determining the influence of age and sex on functional recovery following hypoxic-ischemic brain damage.

Stroke is a disorder affecting the lives of all age groups, and particularly those at the opposite ends of the age spectrum. It is generally believed that the immature brain is more resistant to damage resulting from a hypoxic/ischemic injury, and that it is also more 'plastic' in terms of its ability to recover. Evidence from our laboratory, and a host of others, has indicated, however, that the developing brain may in fact be more sensitive to injury resulting from hypoxia-ischemia. The question remains, however, whether the immature brain has a greater capacity for recovery. In order to determine the relative capability for functional recovery between age groups, a stroke model of comparable injury is required. This paper describes a new rodent model of ischemic injury allowing for comparisons of behavioral recovery spanning the spectrum of ages between newborn and the elderly. Endothelin-1, a potent vasoconstrictor, was stereotactically injected into the brains of 10-, 63-, and 180-day-old Wistar rats, immediately adjacent to the middle cerebral artery. Regionally, the cortex, caudate, and thalamus were most significantly affected, with sparing of the hippocampus. Pathologic assessment indicated a similar degree of injury across age groups affecting the territorial distribution of the middle cerebral artery, with a predominance of damage in the anterior sections of the cortex and caudate (p < 0.05), compared to the posterior sections including the cortex and thalamus. There were no regional differences in the extent of damage between age groups. Interestingly, however, there were significant differences between males and females regarding the overall extent of brain damage (p < 0.05), with males showing greater damage than females. In addition, there were significant regional differences in the extent of damage between males and females, particularly regarding cortical damage (p < 0.05), both anteriorly and posteriorly, and the caudate anteriorly (p < 0.05). Our findings provide an important new model for comparison of brain damage among the entire spectrum of ages affected by stroke. Importantly, this will allow for further investigations regarding both functional recovery and gender difference comparisons. This may have important ramifications for the development of therapeutic interventions that are age and gender specific.

Age Factors↗