Steady-State Analysis of Auditory Evoked Potentials over a Wide Range of Stimulus Repetition Rates: Profile in Children versus Adults

This study profiled auditory steady-state response amplitudes in children (i.e., six to nine years of age) and in adults (i.e., 18 to 35 years of age) over a wide range of repetition rates, specifically a range well embracing component waves of conventionally stimulated and recorded transient auditory evoked responses. Response amplitudes were measured at repetition rates from 0.75 to 80 Hz. Repetition rates of 10 Hz or less have received little attention in the context of the ASSR approach which is speculated to provide technical advantages, if not additional information, to the more traditional transient protocols, at least for some applications as follows: (1) to permit characterization of subject age-dependent amplitudes; (2) to allow an exploratory examination of the effects of repetition rate on response amplitude during natural sleep, to demonstrate if results differed from those obtained when subjects were awake, and (3) to explore the use of both the fundamental and harmonics in the characterization of the response amplitude versus the typical measure of amplitude in transient analysis. Planned comparisons were conducted to evaluate the amplitude differences observed between the age groups (i.e., children and adults) and between arousal conditions (i.e., adults awake and adults asleep) across modulation frequencies. The results of this study show that the amplitude was largest at the two lowest modulation frequencies for both adults and children. Furthermore, response amplitudes for children were significantly higher than those for adults at all modulation frequencies up to 5 Hz. Response amplitudes for adults during sleep also were significantly higher than those responses of adults while awake at 0.75 and 1.25 Hz. Good reliability overall was observed for these response measures in both adults and children. An amplitude measure defined as the harmonic sum yielded results paralleling the profile of response amplitudes as a function of repetition rate that may be extracted from the literature, although with some differences, the significance of which remains to be determined. Of pragmatic importance is that this profile could be determined without subjective wave identification and/or interpretation and thus by a method that is inherently more objective than conventional, transient AEP tests

Sagging Eye Syndrome--an Overlooked Diagnosis

Abstract Background: Sagging Eye Syndrome (SES) is a relatively unknown cause for binocular distance diplopia. SES presents with an acquired comitant or non-comitant small angle esotropia and/or hypotropia commonly occurring in the elderly population. Inferior displacement of the lateral rectus secondary to age-related degeneration of orbital connective tissue and extraocular muscles appears to be responsible for the ocular misalignment. SES patients often present with new onset or progressively worsening distance diplopia, typically warranting neuroimaging. However, through understanding SES, eye care practitioners may identify these cases, avoiding unnecessary imaging studies. Case Report: A 90-year-old male presented with complaints of intermittent horizontal diplopia at distance despite being prescribed prism for presumed decompensating phoria at his most recent eye exam. The patient noted progressing diplopia which appeared worse in right gaze. Full binocular examination revealed a non-comitant esotropia worse at distance than near. External exam revealed prominent deep superior sulci, blepharoptosis, and orbital fat loss bilaterally. Due to the progressive nature and incomitancy of the diplopia, a neuro-ophthalmology consult was obtained, and the patient was diagnosed with SES. A clinical diagnosis was made based on history, adnexal features, and motility patterns distinct to SES, obviating the need for confirmatory imaging. Conclusion: Patients presenting with new onset diplopia secondary to undiagnosed SES may prompt expensive and time-consuming investigations. It is critical that eye care practitioners accurately recognize the signs, symptoms, and clinical features of SES to avoid unwarranted imaging and patient anxiety. This case report reviews the clinical presentation, exam findings, and distinct picture of SES required for diagnosis and necessary to differentiate this condition from more serious neurologic conditions. Treatment and management will be discussed. Note: No identifiable health information was included in this case report. Written informed consent was obtained for patient images

The Deflationary Theory of Ontological Dependence

When an entity ontologically depends on another entity, the former ‘presupposes’ or ‘requires’ the latter in some metaphysical sense. This paper defends a novel view, Dependence Deflationism, according to which ontological dependence is what I call an aggregative cluster concept: a concept which can be understood, but not fully analysed, as a ‘weighted total’ of constructive and modal relations. The view has several benefits: it accounts for clear cases of ontological dependence as well as the source of disagreement in controversial ones; it gives a nice story about the evidential relevance of modal, mereological and set-theoretic facts to ontological dependence; and it makes sense of debates over the relation's formal properties. One important upshot of the deflationary account is that questions of ontological dependence are generally less deep and less interesting than usually thought