When your income drops : sharpen survival skills (1993)

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When your income drops : control stress (1993)

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When your income drops : plan to pay creditors and protect family welfare (1993)

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When your income Drops : take stock of family resources (1993)

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Visual mental imagery during caloric vestibular stimulation.

We investigated high-resolution mental imagery and mental rotation, while the participants received caloric vestibular stimulation. High-resolution visual mental imagery tasks have been shown to activate early visual cortex, which is deactivated by vestibular input. Thus, wepredicted that vestibular stimulation would disrupt high-resolution mental imagery; this prediction was confirmed. In addition, mental rotationtasks have been shown to activate posterior parietal cortex, which is also engaged in the processing of vestibular stimulation. As predicted,we also found that mental rotation is impaired during vestibular stimulation. In contrast, such stimulation did not affect performance of alow-imagery control task. These data document previously unsuspected interactions between the vestibular system and the high-level visualsystem

Vestibular thresholds for yaw rotation about an earth-vertical axis as a function of frequency

Perceptual direction detection thresholds for yaw rotation about an earth-vertical axis were measured at seven frequencies (0.05, 0.1, 0.2, 0.5, 1, 2, and 5Hz) in seven subjects in the dark. Motion stimuli consisted of single cycles of sinusoidal acceleration and were generated by a motion platform. An adaptive two-alternative categorical forced-choice procedure was used. The subjects had to indicate by button presses whether they perceived yaw rotation to the left or to the right. Thresholds were measured using a 3-down, 1-up staircase paradigm. Mean yaw rotation velocity thresholds were 2.8degs−1 for 0.05Hz, 2.5degs−1 for 0.1Hz, 1.7degs−1 for 0.2Hz, 0.7degs−1 for 0.5Hz, 0.6degs−1 for 1Hz, 0.4 degs−1 for 2Hz, and 0.6degs−1 for 5Hz. The results show that motion thresholds increase at 0.2Hz and below and plateau at 0.5Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2Hz and below would be consistent with decreased gain/sensitivity observed in the VOR at lower frequencies. In fact, the measured dynamics are consistent with a high pass filter having a threshold plateau of 0.71degs-1 and a cut-off frequency of 0.23Hz, which corresponds to a time constant of approximately 0.70s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation threshold

Debt, financial stability, and public policy

Debt ; Economic policy ; Economic stabilization

New methods for savings and loans to hedge interest rate risk

Increased interest rate volatility in recent years has led to a greater volatility in profits at savings and loan associations. To help stabilize their profits, some S&L's are implementing interest rate hedging programs. These programs use financial instruments such as interest rate swaps, financial futures and options on financial futures. Because hedging programs introduce their own risks, S&L's should thoroughly examine all aspects of the programs before employing them.Hedging (Finance) ; Savings and loan associations ; Interest rates

Vestibular Perception following Acute Unilateral Vestibular Lesions.

Little is known about the vestibulo-perceptual (VP) system, particularly after a unilateral vestibular lesion. We investigated vestibulo-ocular (VO) and VP function in 25 patients with vestibular neuritis (VN) acutely (2 days after onset) and after compensation (recovery phase, 10 weeks). Since the effect of VN on reflex and perceptual function may differ at threshold and supra-threshold acceleration levels, we used two stimulus intensities, acceleration steps of 0.5°/s(2) and velocity steps of 90°/s (acceleration 180°/s(2)). We hypothesised that the vestibular lesion or the compensatory processes could dissociate VO and VP function, particularly if the acute vertiginous sensation interferes with the perceptual tasks. Both in acute and recovery phases, VO and VP thresholds increased, particularly during ipsilesional rotations. In signal detection theory this indicates that signals from the healthy and affected side are still fused, but result in asymmetric thresholds due to a lesion-induced bias. The normal pattern whereby VP thresholds are higher than VO thresholds was preserved, indicating that any 'perceptual noise' added by the vertigo does not disrupt the cognitive decision-making processes inherent to the perceptual task. Overall, the parallel findings in VO and VP thresholds imply little or no additional cortical processing and suggest that vestibular thresholds essentially reflect the sensitivity of the fused peripheral receptors. In contrast, a significant VO-VP dissociation for supra-threshold stimuli was found. Acutely, time constants and duration of the VO and VP responses were reduced - asymmetrically for VO, as expected, but surprisingly symmetrical for perception. At recovery, VP responses normalised but VO responses remained shortened and asymmetric. Thus, unlike threshold data, supra-threshold responses show considerable VO-VP dissociation indicative of additional, higher-order processing of vestibular signals. We provide evidence of perceptual processes (ultimately cortical) participating in vestibular compensation, suppressing asymmetry acutely in unilateral vestibular lesions

Determining thresholds using adaptive procedures and psychometric fits: evaluating efficiency using theory, simulations, and human experiments

When measuring thresholds, careful selection of stimulus amplitude can increase efficiency by increasing the precision of psychometric fit parameters (e.g., decreasing the fit parameter error bars). To find efficient adaptive algorithms for psychometric threshold (“sigma”) estimation, we combined analytic approaches, Monte Carlo simulations, and human experiments for a one-interval, binary forced-choice, direction-recognition task. To our knowledge, this is the first time analytic results have been combined and compared with either simulation or human results. Human performance was consistent with theory and not significantly different from simulation predictions. Our analytic approach provides a bound on efficiency, which we compared against the efficiency of standard staircase algorithms, a modified staircase algorithm with asymmetric step sizes, and a maximum likelihood estimation (MLE) procedure. Simulation results suggest that optimal efficiency at determining threshold is provided by the MLE procedure targeting a fraction correct level of 0.92, an asymmetric 4-down, 1-up staircase targeting between 0.86 and 0.92 or a standard 6-down, 1-up staircase. Psychometric test efficiency, computed by comparing simulation and analytic results, was between 41 and 58 % for 50 trials for these three algorithms, reaching up to 84 % for 200 trials. These approaches were 13–21 % more efficient than the commonly used 3-down, 1-up symmetric staircase. We also applied recent advances to reduce accuracy errors using a bias-reduced fitting approach. Taken together, the results lend confidence that the assumptions underlying each approach are reasonable and that human threshold forced-choice decision making is modeled well by detection theory models and mimics simulations based on detection theory models.National Institute on Deafness and Other Communication Disorders (U.S.) (Grants R01-DC04158, R56-DC12038 and R03-DC013635