Amplitude modulation depth discrimination of a sinusoidal carrier: effect of stimulus duration.

Discrimination of the change in depth of sinusoidal amplitude modulation (AM) was investigated as a function of stimulus duration. The carrier frequency was 4000 Hz, the standard modulation depth (m) was either 0.1, 0.

The modulated-unmodulated difference: effects of signal frequency and masker modulation depth.

The masked threshold for a signal is often times lower when the masker is modulated than when it is unmodulated. The difference in masked thresholds is referred to as the modulated-unmodulated difference, or MUD. The purpose of the present study was to follow up on the results of a previous study [Bacon et al.

Calretinin neurons in human medial prefrontal cortex (areas 24a,b,c, 32', and 25).

The calcium-binding protein calretinin (CR) is present in a subpopulation of local-circuit neurons in the mammalian cerebral cortex containing gamma-aminobutyric acid. This light microscopic investigation provides a detailed qualitative and quantitative morphological analysis of CR-immunoreactive (CR+) neurons in the medial prefrontal cortex (mPFC; areas 24a,b,c, 32', and 25) of the normal adult human. The morphology of CR+ neurons and their areal and laminar distributions were consistent across human mPFC.

Effect of low-frequency gain reduction on speech recognition and its relation to upward spread of masking.

Speech recognition was measured in listeners with normal hearing and in listeners with sensorineural hearing loss under conditions that simulated hearing aid processing in a low-pass and speech-shaped background noise. Differing amounts of low-frequency gain reduction were applied during a high-frequency monosyllable test and a sentence level test to simulate the frequency responses of some commercial hearing aids. The results showed an improvement in speech recognition with low-frequency gain reduction in the low-pass noise, but not in the speech-shaped background noise.

Masking by modulated and unmodulated noise: effects of bandwidth, modulation rate, signal frequency, and masker level.

The threshold for a sinusoidal signal masked by a band of noise is often times lower when the masking noise is modulated than when it is unmodulated. The difference in masked thresholds is referred to as the modulated-unmodulated difference, or MUD. These present experiments examined the effects of masker bandwidth, masker rate, and masker level on the MUD at several different signal frequencies.

Calcineurin immunoreactivity in prelimbic cortex (area 32) of the rat.

Calcineurin (CN) is a Ca2+/calmodulin-dependent phosphatase present in brain tissue. In this immunocytochemical study of rat prelimbic cortex (area 32), a gradient of CN immunolabelling was found in the somata and processes of pyramidal cells and in interneurones. Some apical dendritic spines were weakly immunoreactive.

Local-circuit neurones in the medial prefrontal cortex (areas 25, 32 and 24b) in the rat: morphology and quantitative distribution.

This paper is a light microscopical study describing the detailed morphology and quantitative distribution of local circuit neurones in areas 25, 32, and 24b of the medial prefrontal cortex (mPFC) in the rat. Cortical interneurones were identified immunocytochemically by their expression of calretinin (CR), parvalbumin (PV), and calbindin D-28k (CB) immunoreactivity. Neurones immunoreactive for gamma-aminobutyric acid (GABA) were also investigated, as were interneurones containing reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity.

Vasoactive intestinal polypeptide containing neurones in monkey medial prefrontal cortex (mPFC): colocalisation with calretinin.

Neurones immunoreactive for vasoactive intestinal polypeptide (VIP) were studied in monkey medial prefrontal cortex. The majority (78.0%) of VIP+ neurones were bipolar cells located mainly in layers 2/3.

The organisation of dendritic bundles in the prelimbic cortex (area 32) of the rat.

Using an antibody against microtubule associated protein 2 (MAP-2; a specific marker for neuronal dendrites), this paper reports the structural organisation of pyramidal cell apical dendrites in the rat prelimbic (PL) cortex. In the coronal plane, MAP-2-immunoreactive apical dendrites of pyramidal neurons in layers 5, 3 and 2 were found bundled together as they ascended radially through the cortex. These bundles of dendrites dispersed in upper layer 2 to form apical dendritic tufts in layer 1.

Amygdala input to medial prefrontal cortex (mPFC) in the rat: a light and electron microscope study.

This paper describes the termination pattern and synaptic connectivity of the pathway from the basolateral nucleus of the amygdala (BLA) to the medial prefrontal cortex (mPFC; areas 25, 32, and 24b) of the rat. Discrete injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) were made in the BLA and detailed light microscopical observations made of the distribution of PHA-L labelled fibres and boutons in the mPFC. Labelled fibres were distributed in two tiers: predominantly within deep layer 1/layer 2 and also in layers 5/6.

Localisation of NADPH diaphorase activity and NOS immunoreactivity in astroglia in normal adult rat brain.

This study demonstrates the co-localisation of NADPH diaphorase activity and GFAP immunoreactivity in non-neuronal cells in weakly fixed brain sections from normal adult rats. The presence of GFAP immunoreactivity in these cells indicates that they are astroglia. In addition, cells possessing the morphological characteristics of astroglia were weakly immunoreactive for the endothelial isoform of nitric oxide synthase (eNOS)--these cells also co-localised NADPH diaphorase activity.

The effect of level and relative frequency region on the recovery of overshoot.

Overshoot--in particular, threshold for a signal near masker onset--can be reduced by presenting a stimulus (precursor) just prior to masker onset. The recovery of overshoot can be examined by varying the delay between the offset of the precursor and the onset of the masker, where "recovery" denotes an increase in the threshold for a signal near masker onset. The present study examined the effects of stimulus level and relative frequency region on this recovery.

Local circuit neurons in the medial prefrontal cortex (areas 24a,b,c, 25 and 32) in the monkey: II. Quantitative areal and laminar distributions.

The companion paper (Gabbott and Bacon [1996] J. Comp. Neurol.

Local circuit neurons in the medial prefrontal cortex (areas 24a,b,c, 25 and 32) in the monkey: I. Cell morphology and morphometrics.

This paper provides a comprehensive morphological description of local circuit neurons in the medial prefrontal cortex (mPFC: areas 24a, 24b, 24c, 25 and 32) of the monkey. Cortical interneurons were identified immunocytochemically by the expression of the calcium binding proteins calretinin (CR), parvalbumin (PV) and calbindin D-28k (CB). Interneurons were also identified using GABA immunocytochemistry.

A Randomized Multicenter Trial Comparing and Efficacy of Simvastatin and Fluvastatin.

BACKGROUND: Inhibitors of hydroxymethylglutaryl co-enzyme A reductase are widely used for the treatment of hypercholesterolemia. Physicians and third-party payers need an accurate measure of their relative potency and hypolipidemic efficacy. We have therefore compared simvastatin against fluvastatin, the newest member of this class.

Co-localisation of NADPH diaphorase activity and GABA immunoreactivity in local circuit neurones in the medial prefrontal cortex (mPFC) of the rat.

This study provides evidence that neurones in the medial prefrontal cortex of the rat (mPFC areas 24b, 25, and 32) containing strong NADPH diaphorase reactivity also contain GABA immunoreactivity. Also demonstrated is the co-localisation of NADPH diaphorase activity with immunoreactivity for the neuronal isoform of nitric oxide synthase (nNOS) in mPFC neurones. Qualitative and quantitative analyses in the light and electron microscopes indicate that strongly NADPH diaphorase reactive cells are a subpopulation of GABAergic local circuit neurones and constitute a very small proportion (0.

Dendritic spine density of NADPH diaphorase reactive neurons in the medial prefrontal cortex (mPFC) of the rat.

The density of spines has been calculated over the processes of NADPH diaphorase reactive neurons in the medial prefrontal cortex (mPFC) of the rat. Quantitative data indicate that diaphorase reactive dendrites ranged from being virtually aspiny to possessing moderate numbers of spines (0.66 +/- 0.

Some factors influencing comodulation masking release and across-channel masking.

The purpose of this study was to determine whether comodulation masking release (CMR) and across-channel masking (ACM) are by-products of a similar across-channel mechanism. This was addressed by examining how the two are affected by stimulus manipulations expected to influence their magnitude. Subjects were required to detect a 1000-Hz signal in the presence of a masker that consisted of a 1000-Hz (on-frequency) component alone or that component and up to six flanking components (500, 600, 700, 1300, 1400, and 1500 Hz).

Effects of combining maskers in modulation detection interference.

The threshold for detecting 10-Hz amplitude modulation of a 2000-Hz carrier was measured in quiet, in the presence of an unmodulated masker, and in the presence of an amplitude-modulated masker. Two experiments were run; in each, the masker consisted of one or two sinusoidal carriers (chosen from among the frequencies of 800, 1600, 2400, and 3200 Hz). In experiment 1, the modulation rate of the masker ranged from 2 to 80 Hz.

Two types of interneuron in the dorsal lateral geniculate nucleus of the rat: a combined NADPH diaphorase histochemical and GABA immunocytochemical study.

The rationale for this study was to provide a comprehensive light microscopical description of the morphology of diaphorase-reactive neurons and neuropil elements in the dorsal lateral geniculate nucleus (dLGN) of the rat. An additional objective was to quantitatively assess whether a subpopulation of the diaphorase-reactive neurons, previously shown to be GABA-immunoreactive, constitute a distinct type of local-circuit neuron in the rat dLGN. Diaphorase activity was localised in a population of predominantly bipolar fusiform neurons.

Multiple factors determine the sex ratio of postpartum-conceived Norway rat litters.

When Norway rat litters are nursed communally, postpartum-conceived litters born asynchronously are female biased at birth. To determine if one or more mechanisms produced this sex ratio bias, we studied litters conceived at a postpartum estrus, and systematically varied the presence or absence of a litter suckling during gestation. Four different factors biased the sex ratio of postpartum-conceived litters.

Monotic and dichotic modulation detection interference in practiced and unpracticed subjects.

The threshold for detecting 10-Hz amplitude modulation of a 1-kHz carrier was measured in quiet and in the presence of a 4-kHz masker carrier that was either unmodulated or amplitude modulated at a depth of 1.0 and at rates from 2 to 80 Hz. The signal and masker were presented to the same ear (monotic condition) or to opposite ears (dichotic condition), and the subjects either had no previous experience with psychoacoustic experiments (n = 10) or had from 16 to about 70 h of experience with modulation-detection tasks (n = 4).

Intensity discrimination and increment detection at 16 kHz.

When presented for several seconds, a very high-frequency tone can decay to inaudibility in subjects with normal hearing. The purpose of the present study was to determine how such a tone behaves once it is inaudible. Intensity difference limens (DLs) at 16 kHz were measured for gated (audible) and continuous (inaudible) pedestals over a range of pedestal sensation levels from about 0-60 dB, and were compared with those obtained in the same two subjects at 1 kHz [N.

An oriented framework of neuronal processes in the ventral lateral geniculate nucleus of the rat demonstrated by NADPH diaphorase histochemistry and GABA immunocytochemistry.

This study investigated the morphology and quantitative distribution of neurons containing NADPH diaphorase activity in the ventral lateral geniculate nucleus of the rat. The pattern of diaphorase staining revealed a strongly reactive lateral subdivision and a weakly staining medial subdivision. A characteristic feature of the diaphorase staining in the lateral part was its "stripe-like" appearance.