Ray Meddis

A prospective evaluation of in-hospital counselling for first time myocardial infarction men

Self-ratings of anxiety and depression were studied over six months in 60 male patients, under 66 yr of age, who were admitted to a coronary care unit with a first time acute myocardial infarction. Patients were randomly assigned to either a treatment group, where they received a simple programme of in-hospital counselling in addition to routine care, or to a control group, where they received routine care only. All patients completed the Hospital Anxiety and Depression scale and a battery of visual analogue scales measuring anxiety on a range of topics related to recovery from a myocardial infarction. Patients who received in-hospital counselling reported statistically significantly less anxiety and depression than those who received routine care alone. This effect was sustained for six months after leaving hospital. It is concluded that a simple programme of in-hospital counselling, provided by a coronary care nurse, is efficacious and should be routinely offered to first myocardial infarction patients in hospital.

Wives' responses to counselling early after myocardial infarction.

Self-ratings of anxiety and depression were studied over six months in 60 wives of first time myocardial infarction patients. Couples were randomly assigned to either a treatment group, where they received a simple programme of education and psychological support in addition to routine care, or to a control group, where they received routine care only. All wives completed the Hospital Anxiety and Depression scale and a battery of visual analogue scales measuring anxiety on a range of topics related to recovery from a heart attack. Wives in the treatment group reported statistically significantly less anxiety than controls. This effect was sustained for six months after the counselling. It is concluded that a simple programme of in hospital counselling is efficacious and should be routinely offered to the wives of coronary patients.

A computer model of auditory stream segregation

A computer model is described which simulates some aspects of auditory stream segregation. The model emphasizes the explanatory power of simple physiological principles operating at a peripheral rather than a central level. The model consists of a multi-channel bandpass-filter bank with a “noisy” output and an attentional mechanism that responds selectively to the channel with the greatest activity. A “leaky integration” principle allows channel excitation to accumulate and dissipate over time. The model produces similar results to two experimental demonstrations of streaming phenomena, which are presented in detail. These results are discussed in terms of the “emergent properties” of a system governed by simple physiological principles. As such the model is contrasted with higher-level Gestalt explanations of the same phenomena while accepting that they may constitute complementary kinds of explanation.

Time decay of auditory stream biasing

In an experiment designed to investigate the time decay of auditory stream biasing (ASB), subjects were required to listen to a 10-sec induction sequence of repeated tones (AAAA …) designed to bias the listener’s percept toward hearing an A stream. The induction sequence was followed immediately by a silent interval (0–8 sec), and then a short ABAB … test sequence. To measure the amount of ASB remaining at the end of the silent interval, subjects were asked to indicate whether the test sequence was temporally coherent or had segregated into separate A and B streams. A plot of the mean number of segregation responses against silent-interval duration indicated that the overall time decay of ASB can be described by an exponential decay function with a time constant of t = 3.84 sec, with musicians having a longer time constant (τ = 7.84 sec) than nonmusicians (τ = 1.42 sec). The length of the time constants for musicians and nonmusicians suggests that the mechanism responsible for ASB is associated with long auditory storage and that future experiments investigating auditory streaming phenomena should use interstimulus intervals of at least 8 sec.

The role of binaural and fundamental frequency difference cues in the identification of concurrently presented vowels

The relative importance of voice pitch and interaural difference cues in facilitating the recognition of both of two concurrently presented synthetic vowels was measured. The interaural difference cues used were an interaural time difference (400 μsec ITD), two magnitudes of interaural level difference (15 dB and infinite ILD), and a combination of ITD and ILD (400 μsec plus 15 dB). The results are analysed separately for those cases where both vowels are identical and those where they are different. When the two vowels are different, a voice pitch difference of one semitone is found to improve the percentage of correct reports of both vowels by 35.8% on average. However, the use of interaural difference cues results in an improvement of 11.5% on average when there is a voice pitch difference of one semitone, but only a non-significant 0.1% when there is no voice pitch difference. When the two vowels are identical, imposition of either a voice pitch difference or binaural difference reduces performance, in a subtractive manner. It is argued that the smaller size of the interaural difference effect is not due to a “ceiling effect” but is characteristic of the relative importance of the two kinds of cues in this type of experiment. The possibility that the improvement due to interaural difference cues may in fact be due to monaural processing is discussed. A control experiment is reported for the ITD condition, which suggests binaural processing does occur for this condition. However, it is not certain whether the improvement in the ILD condition is due to binaural processing or use of the improvement in signal-to-noise ratio for a single vowel at each ear.

Lateralization of very-short-duration tone pulses of low and high frequencies

The position and image-width of the simultaneous images produced by very short tone pulses were measured as a function of interaural time difference (ITD) at both low- (250 and 800 Hz) and high- (2500 and 8000 Hz) frequencies using a direct-estimation technique. Primary images are lateralized towards the ear receiving the leading stimulus. At low frequencies image position is proportional to interaural phase-difference (IPD) below 90° and remains at the lead-ear for larger values. At high frequencies image position is proportional to ITD up to 500–1000 μsec. Secondary images are reported on the opposite side of the head for IPDs greater than 180° at low frequencies, and at ITDs greater than 500 μsec at high frequencies. Image width is approximately constant for all ITDs and both images at a given frequency, but becomes more compact as frequency increases. The data are discussed in terms of onset cues and stimulus fine-structure cues. The best explanation is in terms of an onset mechanism, but one that is calibrated in terms of IPD at low frequencies. The existence of double images is explained in terms of a breakdown in the mechanism determining fusion.

Computer Simulation of Gestalt Auditory Grouping by Frequency Proximity

A computer model is described that is able to reproduce two examples of auditory-streaming phenomena normally accounted for by the Gestalt auditory grouping principle of proximity. These are: 1) the fission boundary of human listeners, and 2) the stream-organisation process exhibited by human listeners when presented with ABC tone sequences. Whereas auditory-streaming phenomena are generally accounted for in terms of an auditory scene-analysis process that works using Gestalt perceptual principles (e.g. proximity, good continuation), the operation of the model suggests that some Gestalt auditory grouping may be the product of low-level processes, and that physiological and peripheral-channelling factors are responsible for Gestalt auditory grouping by frequency proximity.

The response of guinea pig auditory-nerve fibres with high spontaneous discharge rates to increments in intensity

We have re-examined the response of auditory-nerve fibres with high spontaneous discharge rates to increments in intensity as a function of the delay of the increment. In agreement with previous studies, the response measured over a relatively long time window (10 ms), emphasising the properties of short-term adaptation, did not decrease with the delay of the increment. However, the response to an increment in intensity, measured over a short time window (0.64 ms), was significantly larger when the increment was coincident with the stimulus onset than when it was delayed by either 5, 10 or 15 ms.

Non-Linearity in a Computational Model of the Response of the Basilar Membrane

We are interested in modelling human response to speech signals with particular reference to selective attention. We intend that our models should use principles derived from anatomy and physiology as far as possible. Accordingly, a balance has to be struck hetween available computational power and the need to model all the important subsidiary processes such as middle- and outer- ear effects, basilar membrane response, inner hair-cell response, interactions among neurons in the bminstem nuclei, etc .. Despite the computational overhead of taking it into account. the nonlinearity of the response of the inner ear to sound is important to an understanding of human speech processing for at least two reasons. Firstly, we know that distortion products influence pitch perception - the so-called second effect of pitch shift (Schouten e/ al., 1962) - and pitch is an important element in the segregation of sounds. Secondly, the nonlinear response of the cochlea has important implications for the representation of speech sounds (Miller and Sachs, 1983).

The Electronic Ear

In this chapter we propose to review recent developments and to establish an achievable research agenda for developing VLSI models of auditory signal processing in the mammalian brainstem. Considerable progress can be reported for models of the transduction of acoustic signals into the electrical response of auditory nerve fibres. A useful start has also been made in developing circuits to represent individual nerve cells similar to those found in the auditory brainstem. Only tentative beginnings have been made in the construction of massively parallel circuits to represent the activity of large ensembles of auditory nerve cells but these are enough to establish the feasibility of the enterprise. This progress in the field of electronic modelling capability has been accompanied by a substantial increase in our knowledge of the detailed functioning of individual nerve cells in the early stages of the auditory signal processing system. The time is therefore right for a substantial investment of effort in the development of these new modelling technologies.