The effect of visors on head and facial injury in National Hockey League players.

There has been an increase in the number of concussions sustained by players in the National Hockey League (NHL). While wearing a helmet is now required by the NHL, the face visor remains optional. It is unknown to what degree face visors influence concussion, other head injury and eye-injury rates at the professional level. Data from the 2001-2002 NHL season were examined. It was found that wearing a face visor did not significantly influence the prevalence of concussion. Visor protection did, however, minimise eye-injuries and other, non-concussion head injuries. These data suggest that, while a visor may prevent some head and eye-injuries, other measures may be necessary to reduce the number of concussions.

Absolute pitch and planum temporale.

An increased leftward asymmetry of the planum temporale (PT) in absolute-pitch (AP) musicians has been previously reported, with speculation that early exposure to music influences the degree of PT asymmetry. To test this hypothesis and to determine whether a larger left PT or a smaller right PT actually accounts for the increased overall PT asymmetry in AP musicians, anatomical magnetic resonance images were taken from a right-handed group of 27 AP musicians, 27 nonmusicians, and 22 non-AP musicians. A significantly greater leftward PT asymmetry and a significantly smaller right absolute PT size for the AP musicians compared to the two control groups was found, while the left PT was only marginally larger in the AP group. The absolute size of the right PT and not the left PT was a better predictor of music group membership, possibly indicating "pruning" of the right PT rather than expansion of the left underlying the increased PT asymmetry in AP musicians. Although early exposure to music may be a prerequisite for acquiring AP, the increased PT asymmetry in AP musicians may be determined in utero, implicating possible genetic influences on PT asymmetry. This may explain why the increased PT asymmetry of AP musicians was not seen in the group of early beginning non-AP musicians.

Discrimination of spatial relations and features in faces: effects of inversion and viewing duration.

We studied discrimination of changes in eye position, mouth position, and eye colour at viewing durations ranging from 1 second to unlimited time. With upright faces, perception was rapid and did not improve above 2 seconds viewing time. Face inversion impaired discrimination of mouth position significantly, eye position slightly, but not eye colour. The 'inversion effect' for mouth position decreased with increasing stimulus duration, and disappeared when the subject knew that the only change in a trial was in mouth position. A subsequent experiment showed that the inversion impairment in the mouth region was not specific to spatial position but affected mouth colour to a lesser degree. When the mouth region was made more salient by increasing the frequency of mouth change trials, the inversion effect for mouth position decreased, and correlated with an increase in inversion effect for eye position but not eye colour. We conclude that the dominant effect of face inversion upon perception is decreased discrimination in less salient facial regions, that this impairment lessens with increasing viewing time, and that it affects both features and their spatial relations, though the effect on the latter is greater. These results are consistent with greater dependence on a serial component search strategy in inverted faces.

Interhemispheric asymmetry of motor cortical excitability in major depression as measured by transcranial magnetic stimulation.

BACKGROUND: Neuroimaging studies of major depressive disorder (MDD) indicate interhemispheric differences in prefrontal cortical activity (right greater than left). AIMS: To investigate whether there are any interhemispheric differences of motor cortical excitability in MDD. METHOD: Eight patients with treatment-refractory MDD off medication were assessed for the severity of their depression, and transcranial magnetic stimulation studies (bilateral motor threshold and paired-pulse studies) were conducted. Eight normal controls were also studied. RESULTS: MDD patients showed significant interhemispheric differences in motor threshold and paired-pulse curves, both of which showed lower excitability on the left hemisphere. Such differences were absent in controls. CONCLUSIONS: Our findings may aid the further understanding of the neurophysiology underlying MDD.

Interindividual variability of the modulatory effects of repetitive transcranial magnetic stimulation on cortical excitability.

Repetitive transcranial magnetic stimulation (rTMS) appears to have effects on cortical excitability that extend beyond the train of rTMS itself. These effects may be inhibitory or facilitatory and appear to depend on the frequency, intensity, duration and intertrain interval of the rTMS. Many studies assume facilitatory effects of high-frequency rTMS and inhibitory effects of low-frequency rTMS. Nevertheless, the interindividual variability of this modulation of cortical excitability by rTMS has not been systematically investigated. In this study, we applied 240 pulses of rTMS at 90% of the subjects' motor threshold to their motor cortex at different frequencies (1, 10, 15 and 20 Hz) and examined the effects on motor evoked potentials (frequency tuning curve). Although the averaged group data showed a frequency-dependent increase in cortical excitability, each subject had a different pattern of frequency tuning curve, i.e. a different modulatory effect on cortical excitability at different rTMS frequencies. The interindividual variability of these modulatory effects was still high, though less so, when the number of rTMS pulses was increased to 1,600. These findings illustrate the degree of variability of the rTMS effects in the human brain.

Tactile spatial resolution in blind braille readers.

OBJECTIVE: To determine if blind people have heightened tactile spatial acuity. BACKGROUND: Recently, studies using magnetic source imaging and somatosensory evoked potentials have shown that the cortical representation of the reading fingers of blind Braille readers is expanded compared to that of fingers of sighted subjects. Furthermore, the visual cortex is activated during certain tactile tasks in blind subjects but not sighted subjects. The authors hypothesized that the expanded cortical representation of fingers used in Braille reading may reflect an enhanced fidelity in the neural transmission of spatial details of a stimulus. If so, the quantitative limit of spatial acuity would be superior in blind people. METHODS: The authors employed a grating orientation discrimination task in which threshold performance is accounted for by the spatial resolution limits of the neural image evoked by a stimulus. The authors quantified the psychophysical limits of spatial acuity at the middle and index fingers of 15 blind Braille readers and 15 sighted control subjects. RESULTS: The mean grating orientation threshold was significantly (p = 0.03) lower in the blind group (1.04 mm) compared to the sighted group (1.46 mm). The self-reported dominant reading finger in blind subjects had a mean grating orientation threshold of 0.80 mm, which was significantly better than other fingers tested. Thresholds at non-Braille reading fingers in blind subjects averaged 1.12 mm, which were also superior to sighted subjects' performances. CONCLUSION: Superior tactile spatial acuity in blind Braille readers may represent an adaptive, behavioral correlate of cortical plasticity.

Modulation of corticospinal excitability by repetitive transcranial magnetic stimulation.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) is able to modulate the corticospinal excitability and the effects appear to last beyond the duration of the rTMS itself. Different studies, employing different rTMS parameters, report different modulation of corticospinal excitability ranging from inhibition to facilitation. Intraindividual variability of these effects and their reproducibility are unclear. METHODS: We examined the modulatory effects of rTMS to the motor cortex at various frequencies (1, 10, 20 Hz) and at different time-points in twenty healthy volunteers. RESULTS: We observed significant inhibition of MEPs following 1 Hz rTMS and significant facilitation of MEPs following 20 Hz rTMS for both day1 and day 2. Interestingly, at 1 Hz and 20 Hz rTMS, the modulatory effect produced by rTMS was greater on day 2. However, there was no significant change in corticospinal excitability following 10 Hz rTMS neither on day 1 nor day 2. CONCLUSION: Our findings raise questions as to how stimulation parameters should be determined when conducting studies applying rTMS on multiple days, and in particular, studies exploring rTMS as a treatment modality in neuropsychiatric disorders.

Hand response differences in a self-face identification task.

Evidence has indicated that the right frontal cortex is preferentially involved in self-face recognition. To test this further, we employed a face identification task and examined hand response differences (N=10). Pictures of famous faces were combined with pictures of the participants' faces (self) and their co-workers' faces (familiar). These images were presented as a 'movie' in which one face transformed into another. Under the first instruction set, the movies began with either the participant's face or a co-worker's face, and the sequences gradually morphed into a famous face. When told to stop the movie when the face in the sequence became famous, a significantly later 'frame' was identified when the movies were composed of self-faces and the participants responded with their left hand. When the movies started with the famous faces and participants had to stop the movie when it became their own or their familiar co-worker's image (Instruction set 2), a significantly earlier frame was identified in the 'Self: Left hand' condition. The data suggest that participants are inclined to identify images as their own when the right hemisphere is preferentially accessed.

Transcranial magnetic stimulation of primary motor cortex affects mental rotation.

Neuroimaging studies have shown that motor structures are activated not only during overt motor behavior but also during tasks that require no overt motor behavior, such as motor imagery and mental rotation. We tested the hypothesis that activation of the primary motor cortex is needed for mental rotation by using single- pulse transcranial magnetic stimulation (TMS). Single-pulse TMS was delivered to the representation of the hand in left primary motor cortex while participants performed mental rotation of pictures of hands and feet. Relative to a peripheral magnetic stimulation control condition, response times (RTs) were slower when TMS was delivered at 650 ms but not at 400 ms after stimulus onset. The magnetic stimulation effect at 650 ms was larger for hands than for feet. These findings demonstrate that (i) activation of the left primary motor cortex has a causal role in the mental rotation of pictures of hands; (ii) this role is stimulus-specific because disruption of neural activity in the hand area slowed RTs for pictures of hands more than feet; and (iii) left primary motor cortex is involved relatively late in the mental rotation process.

Alexia for Braille following bilateral occipital stroke in an early blind woman.

Recent functional imaging and neurophysiologic studies indicate that the occipital cortex may play a role in Braille reading in congenitally and early blind subjects. We report on a woman blind from birth who sustained bilateral occipital damage following an ischemic stroke. Prior to the stroke, the patient was a proficient Braille reader. Following the stroke, she was no longer able to read Braille yet her somatosensory perception appeared otherwise to be unchanged. This case supports the emerging evidence for the recruitment of striate and prestriate cortex for Braille reading in early blind subjects.

Self-face identification is increased with left hand responses.

Evidence suggests that autobiographical memory, self-related semantic category judgements, and self-identification tasks may be lateralised, with preferential activity in the right anterior temporal and prefrontal cortex. To test this hypothesis, participants (N=10) were presented with morphed images of themselves (self) combined with a famous face. A further set of images was generated in which the face of one of the participant's co-workers (familiar) was combined with a famous face. When compared to morphed images composed of a familiar face, the participants identified images less often as being famous if the images were composed of self, but only when responding with their left hands. This greater "self-effect" found in left-hand responses may imply that when the right hemisphere is preferentially active, participants have a tendency to refer images to self. These data provide further support for a preferential role of the right hemisphere in processing self-related material.

Left hand advantage in a self-face recognition task.

Subjects were exposed to pictures of self and others (e.g., friend, stranger, and famous people) to determine if there was an advantage in reaction time and accuracy in identifying the self. It was found that upright and inverted self-faces were identified more rapidly than non-self faces when subjects responded with their left hand, which in other tasks has corresponded with contralateral hemispheric dominance. These data suggest that self-recognition may be correlated with neural activity in the right hemisphere, and that the differences observed may not be unique to self-face recognition. These results are in agreement with previous research indicating that self-directed awareness is correlated with right prefrontal activity.

Transcranial magnetic stimulation: studying the brain-behaviour relationship by induction of 'virtual lesions'.

Transcranial magnetic stimulation (TMS) provides a non-invasive method of induction of a focal current in the brain and transient modulation of the function of the targeted cortex. Despite limited understanding about focality and mechanisms of action, TMS provides a unique opportunity of studying brain-behaviour relations in normal humans. TMS can enhance the results of other neuroimaging techniques by establishing the causal link between brain activity and task performance, and by exploring functional brain connectivity.

The role of area 17 in visual imagery: convergent evidence from PET and rTMS.

Visual imagery is used in a wide range of mental activities, ranging from memory to reasoning, and also plays a role in perception proper. The contribution of early visual cortex, specifically Area 17, to visual mental imagery was examined by the use of two convergent techniques. In one, subjects closed their eyes during positron emission tomography (PET) while they visualized and compared properties (for example, relative length) of sets of stripes. The results showed that when people perform this task, Area 17 is activated. In the other, repetitive transcranial magnetic stimulation (rTMS) was applied to medial occipital cortex before presentation of the same task. Performance was impaired after rTMS compared with a sham control condition; similar results were obtained when the subjects performed the task by actually looking at the stimuli. In sum, the PET results showed that when patterns of stripes are visualized, Area 17 is activated, and the rTMS results showed that such activation underlies information processing.

The effects of family history, sobriety length, and drinking history in younger alcoholics on P300 auditory-evoked potentials.

Event-related potentials (ERPs) have been shown to be different between alcoholics and non-alcoholics. Of particular interest to investigators has been the P300 wave. Because it has been shown that alcohol-induced neural damage can alter P300 waves, particularly amplitude, we attempted to examine alcoholics who most likely suffered little damage because they drank heavily for relatively few years (mean = 6.9 years). The effects of long-term sobriety (mean = 5.0) were also investigated to determine if cognitive functioning, as measured by auditory-evoked P300 waves, varies with increased abstinence. Because family history for alcoholism has also been shown to influence P300 amplitude and latency, alcoholics and controls with and without family history were examined. The alcoholic group had significantly longer latencies in P300 measures in both the family history positive and negative groups; P300 amplitudes between alcoholics and non-alcoholics did not vary, regardless of family history. P300 waves were unaffected by sobriety length or drinking history. The results support the hypothesis that P300 differences can be seen between alcoholics and those at risk for alcoholism.

Pediatric mechanical ventilation technology.

An in-depth examination of ventilators currently marketed for the pediatric population and the technology associated with each is provided with this article. Also included is a discussion of an "ideal pediatric ventilator" and its application to the pediatric intensive care patient. Triggering, cycling, and limiting variability, costs, and special features currently available are detailed.

Staged below-knee amputations for septic peripheral lesions due to ischaemia.

Preservation of the knee joint is of paramount importance in lower limb amputation for ischaemia. Clinical predictors of healing are unreliable in patients with septic peripheral lesions due to ischaemia. Seventy-three patients in whom a below-knee amputation was considered likely to heal, based on the temperature and appearance of the skin and bleeding from skin and muscle flaps, were divided into two groups. Twenty-nine (Group A) had a primary below-knee (BK) amputation at the site of election with delayed primary skin closure, while 44 patients (Group B) initially had a guillotine BK amputation below the site of election, with elective amputation at the appropriate level once infection had been eradicated (4-5 days later). The groups were similarly matched with regard to level of occlusive arterial disease, nature of ischaemic lesions and operative risk factors. There was no significant difference in the overall operative mortality in Group A (6.7 per cent) compared with Group B (11.4 per cent) (P greater than 0.05). There was a significantly higher above-knee revision rate in Group A survivors (33.3 per cent) compared with Group B (7.7 per cent) (P less than 0.01) due to non-viability and uncontrolled sepsis of the BK amputation site. The presence or absence of a palpable femoral or popliteal pulse had no significant influence on healing in either group.