Bright light treatment decreases depression in institutionalized older adults: a placebo-controlled crossover study.

BACKGROUND: An important parallel exists between patients with seasonal affective disorder and institutionalized older adults. Many older patients, as a result of global physical decline and immobility, are confined to their rooms, experiencing little natural sunlight. Thus, institutionalized older adults are at risk for chronic light deprivation. Testing the hypothesis that chronic light deprivation might be responsible, at least in part, for some depression among institutionalized older adults, the aim of this study was to investigate the efficacy of morning bright light treatment on depression among older adults residing in a long-term care facility. METHODS: In a placebo controlled, crossover design, participants (N = 10, six women and four men; M age = 83.8) received each of the following: (i) 1 week (5 days) of 10,000 lux (therapeutic dose); (ii) 1 week (5 days) of 300 lux (placebo); or 1 week of no treatment (control). Each week of light treatment was 5 consecutive days, 30 minutes daily, with a wash-out period consisting of 1 week between conditions. RESULTS: Geriatric Depression Scale (GDS) scores at baseline during all treatment conditions were positively correlated (r = .81, p < .01) with months of institutionalization, where participants with higher GDS scores experienced more time institutionalized. Scores on the GDS remained unchanged during the placebo and control conditions, but depression scores decreased significantly during the 10,000 lux treatment (pretest GDS M = 15 vs posttest GDS M = 11, p < .01). After the 10,000 lux treatment, 50% of the participants no longer scored in the depressed range. Improvement during the 10,000 lux condition was positively correlated (r = .62, p < .05) to baseline GDS scores, where participants with higher GDS scores experienced greater improvement following the 10,000 lux treatment. CONCLUSIONS: The results of the present study suggest that bright light treatment may be effective among institutionalized older adults, providing nonpharmacological intervention in the treatment of depression. Furthermore, the length of institutionalization may play an important role in determining the efficacy of bright light treatment for older adults in the nursing-home setting.

Photopigments and colour vision in New World monkeys from the family Atelidae.

Most New World monkeys have an X-chromosome opsin gene polymorphism that produces a variety of different colour vision phenotypes. Howler monkeys (Alouatta), one of the four genera in the family Atelidae lack this polymorphism. Instead, they have acquired uniform trichromatic colour vision similar to that of Old World monkeys, apes and people through opsin gene duplication. In order to determine whether closely related monkeys share this arrangement, spectral sensitivity functions that allow inferences about cone pigments were measured for 56 monkeys from two other Atelid genera, spider monkeys (Ateles) and woolly monkeys (Lagothrix). Unlike howler monkeys, both spider and woolly monkeys are polymorphic for their middle- and long-wavelength cone photopigments. However, they also differ from other polymorphic New World monkeys in having two rather than three possible types of middle- and long-wavelength cone pigments. This feature directly influences the relative numbers of dichromatic and trichromatic monkeys.

Uniformity of colour vision in Old World monkeys.

It is often assumed that all Old World monkeys share the same trichromatic colour vision, but the evidence in support of this conclusion is sparse as only a small fraction of all Old World monkey species have been tested. To address this issue, spectral sensitivity functions were measured in animals from eight species of Old World monkey (five cercopithecine species and three colobine species) using a non-invasive electrophysiological technique. Each of the 25 animals examined had spectrally well-separated middle- and long-wavelength cone pigments. Cone pigments maximally sensitive to short wavelengths were also detected, implying the presence of trichromatic colour vision. Direct comparisons of the spectral sensitivity functions of Old World monkeys suggest there are no significant variations in the spectral positions of the cone pigments underlying the trichromatic colour vision of Old World monkeys.

Photopigment basis for dichromatic color vision in cows, goats, and sheep.

Electroretinogram (ERG) flicker photometry was used to measure the spectral properties of cones in three common ungulates-cattle (Bos taurus), goats (Capra hircus), and sheep (Ovis aries). Two cone mechanisms were identified in each species. The location of peak sensitivity of an S-cone mechanism varied from about 444 to 455 nm for the three species; analogous values for an M/L-cone were tightly clumped at about 552-555 nm. Each of these three species has the requisite photopigment basis for dichromatic color vision and they are, thus, similar to other ungulates examined earlier.

Spectral sensitivity of macaque monkeys measured with ERG flicker photometry.

Macaque monkeys are widely used as a model species for investigations of the biology of human vision. Previous measurements suggest that the cone-based spectral sensitivity of these two primates is greatly similar, but perhaps not identical. We measured the photopic spectral sensitivity of 42 male macaque monkeys from two species (Macaca mulatta, M. fascicularis) using an objective index, electroretinogram flicker photometry. The variations among individuals and between the two species were very small and there was no evidence for any significant cone pigment polymorphism in this sample. There are small but systematic differences in spectral sensitivity between macaque monkeys and equivalently tested human subjects--the monkeys were slightly more sensitive to short wavelengths (< 520 nm) and slightly less sensitive to wavelengths longer than this value. The results obtained from the curve fitting of standard photopigment absorption spectra to the spectral-sensitivity functions suggest that the difference between human and macaque monkey spectral sensitivity principally reflects differences in the relative proportions of the long- and middle-wavelength cones in the retinas of the two species.

ERG measurements of the spectral sensitivity of common chimpanzee (Pan troglodytes).

The spectral sensitivity of the common chimpanzee (Pan troglodytes) was measured with electroretinogram (ERG) flicker photometry. Chromatic adaptation conditions were used to establish the presence of S-, M- and L-cone pigments. Each of 26 chimpanzees showed substantial and approximately equivalent adaptational changes over the middle and long wavelengths implying an absence of any significant polymorphic variations in the M- and L-cone pigments. As inferred from ERG measurements, the S-cone pigment of the chimpanzee has a spectral peak of about 430 nm. Chimpanzee spectral sensitivity measurements were compared to those obtained from equivalently tested normal human trichromats. The spectral sensitivity of the two species is very similar, chimpanzees being slightly more sensitive to short wavelength lights and slightly less sensitive to long wavelength lights than human subjects. Curve-fitting analyses suggest that spectral filtering may be lower in the chimpanzee lens than it is in the human lens, and that the L/M cone ratio is lower in the chimpanzee.

Trichromatic colour vision in New World monkeys.

Trichromatic colour vision depends on the presence of three types of cone photopigment. Trichromacy is the norm for all Old World monkeys, apes and humans, but in several genera of New World monkeys, colour vision is strikingly polymorphic. The difference in colour vision between these New and Old World primates results form differing arrangements of the pigment genes on the X chromosome. In Old World primates the three photopigments required for routine trichromatic colour vision are encoded by two or more X-chromosome pigment genes and an autosomal pigment gene. New World monkeys typically have only one X-chromosome pigment gene; multiple alleles allow different types of dichromatic colour vision and, in female heterozygous at this locus, variant forms of trichromatic colour vision. Here we report that multiple X-chromosome pigment genes and trichromatic colour vision are the norm for one genus of platyrrhine monkey, the howler monkey, Alouatta.

Spectral sensitivity, photopigments, and color vision in the guinea pig (Cavia porcellus).

Behavioral discrimination tests and electroretinogram (ERG) flicker photometry were used to measure spectral sensitivity and to define the spectral mechanisms of the guinea pig (Cavia porcellus). Results from these 2 approaches converge to indicate that guinea pig retinas contain rods with peak sensitivity of about 494 nm and 2 classes of cone having peak sensitivities of about 429 nm and 529 nm. The presence of 2 classes of cones suggests a retinal basis for a color vision capacity. Behavioral tests of color vision were conducted that verified this prediction: Guinea pigs have dichromatic color vision with a spectral neutral point centered at about 480 nm. The cone pigment complement of the guinea pig is different from that known to characterize other rodents.

Sensitivity to ultraviolet light in the gerbil (Meriones unguiculatus): characteristics and mechanisms.

In earlier electrophysiological experiments on the Mongolian gerbil (Meriones unguiculatus) evidence was obtained to suggest that the retina of this rodent contains only a single type of cone. The cones were found to have peak sensitivity of about 493 nm. Gerbil rods have peak sensitivity of about 500 nm, yielding a Purkinje shift that is small in magnitude and reversed in direction from that conventionally found among mammals. In a series of experiments we extended electrophysiological and behavioral measurements to include UV stimulation and this reveals a second photopic mechanism. Several pieces of evidence suggest this second mechanism is a cone having peak sensitivity of about 360 nm. Results from adaptation experiments show that the sensitivities of the two cone mechanisms can be independently manipulated, and thus they presumably reflect the operation of two types of cone photopigment. The results from behavioral experiments verify that the gerbil UV mechanism provides information that can be used to make visual discriminations based on intensity differences. A test of color vision additionally suggests that the two cone pigments can support some color discriminations.

Electrophysiological measurements of spectral mechanisms in the retinas of two cervids: white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama).

Electroretinogram (ERG) flicker photometry was used to study the spectral mechanisms in the retinas of white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama). In addition to having a rod pigment with maximum sensitivity (lambda max) of about 497 nm, both species appear to have two classes of photopic receptors. They share in common a short-wavelength-sensitive cone mechanism having lambda max in the region of 450-460 nm. Each also has a cone having peak sensitivity in the middle wavelengths, but these differ slightly for the two species. In white-tailed deer the lambda max of this cone is about 537 nm; for the fallow deer the average lambda max value for this mechanism was 542 nm. Deer resemble other ungulates and many other types of mammal in having two classes of cone pigment and, thus, the requisite retinal basis for dichromatic color vision.

Photopigments and color vision in the nocturnal monkey, Aotus.

The owl monkey (Aotus trivirgatus) is the only nocturnal monkey. The photopigments of Aotus and the relationship between these photopigments and visual discrimination were examined through (1) an analysis of the flicker photometric electroretinogram (ERG), (2) psychophysical tests of visual sensitivity and color vision, and (3) a search for the presence of the photopigment gene necessary for the production of a short-wavelength sensitive (SWS) photopigment. Both electrophysiological and behavioral measurements indicate that in addition to a rod photopigment the retina of this primate contains only one other photopigment type--a cone pigment having a spectral peak ca 543 nm. Earlier results that suggested these monkeys can make crude color discriminations are interpreted as probably resulting from the joint exploitation of signals from rods and cones. Although Aotus has no functional SWS photopigment, hybridization analysis shows that Aotus has a pigment gene that is highly homologous to the human SWS photopigment gene.

Photopigments of dogs and foxes and their implications for canid vision.

Electroretinogram (ERG) flicker photometry was used to examine the photopigment complements of representatives of four genera of Canid: domestic dog (Canis familiaris), Island gray fox (Urocyon littoralis), red fox (Vulpes vulpes), and Arctic fox (Alopex lagopus). These four genera share a common cone pigment complement; each has one cone pigment with peak sensitivity of about 555 nm and a second cone pigment with peak at 430-435 nm. These pigment measurements accord well with the conclusions of an earlier investigation of color vision in the dog, and this fact allows some predictions about color vision in the wild canids. An additional set of measurements place the peak of the dog rod pigment at about 508 nm.

Cone photopigments in nocturnal and diurnal procyonids.

Procyonids are small, New World carnivores distributed among some 6 genera. Electroretinogram (ERG) flicker photometry was used to measure the spectra of the cone photopigments for members of two nocturnal species, the raccoon (Procyon lotor) and the kinkajou (Potos flavus), and a diurnal species, the coati (Nasua nasua). Each of the 3 has a class of cone photopigment with maximum sensitivity in the middle to long wavelengths. The spectral positioning of this cone is different for the three. Whereas the raccoon and kinkajou are monochromatic, the diurnal coati is a dichromat having an additional class of cone photopigment with peak sensitivity close to 433 nm.

Retinal receptors in rodents maximally sensitive to ultraviolet light.

High sensitivity to near-ultraviolet light is a fundamental feature of vision in many invertebrates. Among vertebrates there are some amphibians, birds and fishes that are also sensitive to near-ultraviolet wavelengths. This sensitivity can be achieved through a class of cone photoreceptor containing an ultraviolet-sensitive pigment. Although these receptors were thought not to exist in the eyes of mammals, we now report that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light.

Cold-restraint stress increases rat fecal pellet output and colonic transit.

Increased fecal pellet output that occurs during cold-restraint stress (CRS) was evaluated systematically. Free-feeding rats, which exhibit a reduced occurrence of gastric ulcers under these conditions, were studied. CRS significantly increased fecal pellet production and fluid content. However, the fecal output produced during CRS was not associated with increased gut secretory activity or somatic motor activity associated with cold restraint and did not occur in anesthetized animals. Cold and restraint stress were additive in producing increased fecal output. Significant dose-related decreases in fecal output were produced by drugs that decrease gut transit (i.e., B-HT 920, clonidine, Lomotil, loperamide, and lidamidine). Anticholinergic-antisecretory drugs, antidepressants, and tranquilizers had little effect on fecal output or fluid content. Changes in gastrointestinal transit did not contribute to the increased fecal output during CRS. Transit in the lower small intestine was not altered, but the cecum tended to empty more contents into the large intestine during CRS. Colonic transit was dramatically affected by CRS, which eliminated retrograde transit and produced the evacuation of the majority of colonic contents. The increased colonic transit produced by CRS was decreased in a dose-related fashion by hexamethonium, nifedipine, loperamide, and B-HT 920. In several time-response and drug-inhibition studies during CRS, both fecal pellet output and colonic transit were affected similarly. These data indicate that CRS appears to change central nervous system output to the colon and that it alters colonic smooth muscle motility in a manner that facilitates colonic transit and evacuation. Small intestinal transit is not involved in this phenomenon and is regulated differently during CRS.

Concurrent fixed-ratio and avoidance responding in the squirrel monkey.

Squirrel monkeys maintained concurrent performances appropriate to a fixed-ratio schedule of food reinforcement on one lever and an avoidance schedule on a second lever. The overall rate of responding maintained by either schedule was not systematically affected when the other schedule was discontinued and its lever removed.