Effect of methylphenidate on visual responses in the superior colliculus in the anaesthetised rat: Role of cortical activation

The mechanism of action of psychostimulant drugs in the treatment of Attention Deficit Hyperactivity Disorder is still largely unknown, although recent evidence suggests one possibility is that the drugs affect the superior colliculus (SC). We have previously demonstrated that systemically administered d-amphetamine attenuates/abolishes visual responses to wholefield light flashes in the superficial layers of the SC in anaesthetised rats, and the present study sought to extend this work to methylphenidate (MPH). Anaesthetised rats were administered MPH at a range of doses (or saline) and subjected to monocular wholefield light flashes at two intensities, juxta-threshold and super-threshold. In contrast to d-amphetamine, systemic MPH produced an enhancement of visual activity at both intensities. Methylphenidate was also found to produce activation of the cortical EEG in anaesthetised rats. Furthermore, cortical activation induced by electrical stimulation of the pons was found to enhance visual responses in superficial layers of the SC, and when MPH was paired with pontine-induced cortical activation, the response-enhancing effects of MPH were substantially attenuated. Taken together, the results suggest that the enhancement of visual responses in the superficial layers of the SC by MPH in the anaesthetised rat is an artefact of the drug’s interaction with cortical arousal

Neuroscience: viable applications in education?

As a relatively young science, neuroscience is still finding its feet in potential collaborations with other disciplines. One such discipline is education, with the field of neuroeducation being on the horizon since the 1960s. However, although its achievements are now growing, the partnership has not been as successful as first hopes suggested it should be. Here the authors discuss the theoretical barriers and potential solutions to this, which have been suggested previously, with particular focus on levels of research in neuroscience and their applicability to education. Moreover, they propose that these theoretical barriers are driven and maintained by practical barriers surrounding common language and research literacy. They propose that by overcoming these practical barriers through appropriate training and shared experience, neuroeducation can reach its full potential

A multifaceted approach to neuroscience outreach: meeting the challenges.

UK government targets aim for 50% of 18- to 30-year-olds entering higher education; however, with the vast choice of subjects to study available at this level, it is important to help pupils make informed decisions. As part of this process, awareness of newer fields such as neuroscience, which is not on the syllabus for science at school, needs to be promoted. Various challenges face neuroscientists working with visiting school pupils, including the lack of appropriate teaching resources, the culture and language barrier, and the risk of misinterpretation through oversimplification. The authors have designed a workshop to promote neuroscience and related scientific issues with school pupils aged 16 to 18 years. Pupil feedback showed that awareness of options within science increased after the workshop. The workshop also used resources taken from an undergraduate course successfully, demonstrating that appropriate resources are already available. A practical session using human brains was most popular, with all pupils believing it to be thought provoking and interesting. The final session aimed to challenge stereotypes within science, and despite the lowest pupil ratings overall, the majority agreed this aim was met. Pupils reported that the workshop was interesting and that the information about options within science useful. The most impressive outcome was that, although no pupil recorded less inclination to continue in science following the workshop, 46% said that they were more likely to do so. These data confirm the importance of outreach work for pupils' interest and career choice

Methylphenidate amplifies long-term plasticity in the hippocampus via noradrenergic mechanisms.

Methylphenidate treatment is used for Attention Deficit Hyperactivity Disorder and can improve learning and memory. Previously, improvements were considered a by-product of increased attention; however, we hypothesize that methylphenidate directly alters mechanisms underlying learning and memory, and therefore examined its effects on hippocampal long-term potentiation and long-term depression. Methylphenidate enhanced both mechanisms in the absence of presynaptic changes and in a noradrenalin beta-receptor-dependent manner. These findings can explain both the improved learning and memory and decreased learning selectivity found with methylphenidate treatment and constitute the first demonstration of direct actions of methylphenidate on mechanisms implicated in cognition

Dynamics of neuronal assemblies are modulated by anaesthetics but not analgesics.

BACKGROUND AND OBJECTIVE: Analgesics and anaesthetics have diverse synaptic actions that nonetheless have a common net inhibitory action on neuronal discharge. It is puzzling, therefore, that these two classes of compounds have fundamentally different affects, one blocking pain and the other consciousness. Indeed, beyond the isolated synapse, little is known of the larger scale mechanisms that mediate actual function, for example, transient neuronal assemblies. It was hypothesized that the two classes of drugs might have, respectively, differential effects on transient activation of these assemblies of neurons working together. METHODS: Hippocampal tissue from juvenile Wistar rats was used for in vitro optical imaging with voltage-sensitive dyes and simultaneous field potential recordings. The response to paired pulse stimulation of the hippocampus was recorded in the presence and absence of two types of analgesic (morphine and gabapentin) and two types of anaesthetic (thiopental and propofol). RESULTS: Optical imaging and electrophysiology used in parallel yield quite different results. Most consistently, the imaging technique was able to detect an enhanced period of activation following anaesthetic, but not analgesic application. This effect was not readily seen from electrophysiology field potential recordings. CONCLUSIONS: These findings suggest that, irrespective of the effects of the two drug classes at a synaptic level, the dynamics of transient neuronal assemblies are modified selectively by anaesthetics and not analgesics

Abnormal air righting behaviour in the spontaneously hypertensive rat model of ADHD

The spontaneously hypertensive rat (SHR) is the most commonly used model of attention-deficit hyperactivity disorder (ADHD), displaying the main symptoms of the disorder which are responsive to psychostimulant treatments. Research to date has focused on behavioural tests investigating functioning of the striatum or prefrontal cortex in these rats. However, there is now evidence that the superior colliculus, a structure associated with head and eye movements, may also be dysfunctional in ADHD. Therefore, the aim of this study was to investigate whether the SHR demonstrated impairment in collicular-dependent behaviour. To this end, we examined air righting behaviour, which has previously been shown to be modulated in a height-dependent manner reliant on a functional superior colliculus. We assessed SHR, Wistar Kyotos and Wistars on static righting and air righting at 50 and 10 cm drop heights. There were no differences in static righting, indicating that there were no gross motor differences that would confound air righting. Qualitative analysis of video footage of the righting did not reveal any changes previously associated with collicular damage, unique to the SHR. However, the SHR did show impairment in height-dependent modulation of righting in contrast to both control strains, such that the SHR failed to modulate righting latency according to drop height. This failure is indicative of collicular abnormality. Given that many rodent tests of attentional mechanisms involve head and eye orienting, which are heavily dependent on the colliculus, a collicular dysfunction has strong implications for the type of attentional task used in this strain