Date Thesis Awarded


Access Type

Honors Thesis -- Open Access

Degree Name

Bachelors of Science (BS)




Joshua Burk

Committee Members

Jennifer Bestman

Robin Looft-Wilson


Attention is the ability to process stimuli in the environment and select relevant cues amongst distractors. It is a crucial aspect of the nervous system that engages multiple brain circuits. Neurons that release the neuropeptide orexin are implicated in attention. These neurons originate in the lateral hypothalamus and send projections widely throughout the brain. Evidence suggests orexins modulate attentional mechanisms through interactions with ascending neuromodulatory systems such as the basal forebrain. Experiments manipulating orexin receptors have found a subsequent effect on attention-demanding tasks, with infusions of orexin A enhancing attention in the presence of distractors. In contrast, the blockade of orexin receptors in the basal forebrain has the opposite effect. Furthermore, the aging process is associated with decreased attention, as well as a dysfunctional orexin system. Thus, this study sought to evaluate the effects of the widespread reduction of orexin neurons on sustained attention, and whether this effect was age-dependent. We bilaterally injected rats with orexin-B saporin or a vehicle into the lateral hypothalamus. The performance of lesion animals was compared to their sham counterparts in a shaping procedure, the speed at which they reached the criterion in this procedure, and the visual sustained attention task. We also evaluated whether there were any age-dependent effects. We found no significant effect of lesions on the acquisition of the shaping task nor in the progression analysis. There was a marginally significant difference in acquisition on the attention task. We found no significant differences or interactions between treatment and age for correct rejection percentages in the visual sustained attention task, but a marginally significant result for this same interaction on mean hit percentage. There was a significant difference in the performance of old sham versus lesion rats, with the lesion rats performing better than sham-lesioned animals (contrary to our hypothesis), but no other significant effects. While these results seem counterintuitive given the present literature, there were many factors throughout the experimental procedure that may have contributed to this lack of effect.