Marian C. Diamond's research while affiliated with University of California, Berkeley and other places

Publications (78)

Article
How much influence do brains have in controlling their own destiny during aging? On the one hand, brains can predict the negative sides of the fate of aging with more dementia, more illness, and more social problems over the years and decades ahead. Or, on the other hand, brains can develop a more positive point of view after learning the facts abo...
Article
Full-text available
Environmental enrichment has been reported to aid recovery from behavioral deficits associated with malnutrition in infants and young rats. This study investigated whether corresponding neuroanatomical changes could be detected. Rats were suckled either by well-fed dams or dams malnourished during lactation. At weaning, well-fed males were either h...
Article
Previous studies on human cortical area 39 suggested that neuron:glial ratios differed between the sexes. These findings were the inspiration for the present investigation which dealt with neuronal and glial counts in area 39 in the male and female rat cerebral cortex. Transverse, celloidin or frozen sections, were cut from male and female brains (...
Article
In the first postnatal month, the thickness of the cerebral cortex has different patterns of development in the male and female Long-Evans rat. All areas of the male cortex appear to develop at similar rates, very rapidly for the first 10 days, then more gradually reaching a peak somewhere between 30 and 40 days of age before beginning to decrease...
Article
This experiment studied cerebral cortical morphology in rats living in a crowded-enriched condition. Three groups of 60-day-old, male Long-Evans rats were divided accordingly: 12 rats, 3 per small cage (32 X 20 X 20 cm), standard colony condition; 12 rats in a single, large, enrichment cage with "toys" (70 X 70 X 45 cm), enriched condition; and 36...
Article
This report examines the morphology of the cerebral cortex in the nude mouse (nu/nu) compared with the BALB/c(+/+). Our experiments indicated that the thickness of the lateral frontal lobe was significantly reduced (8%; P less than 0.005) in the 4-month-old, female nude mouse compared with a BALB/c mouse of like sex and age. In addition, the left h...
Article
We determined the concentration of cytosol estrogen receptors in the postnatal, developing right and left cerebral cortices of Long-Evans male or female rats 2 to 3, 7 to 8, 14 to 15, and 25 to 26 days of age. Under anesthesia, the rats were gonadectomized and 24 h later they were killed by decapitation, and the dorsal right and left cerebral corti...
Article
Neuron:glial ratios were determined in specific regions of Albert Einstein's cerebral cortex to compare with samples from 11 human male cortices. Cell counts were made on either 6- or 20-micron sections from areas 9 and 39 from each hemisphere. All sections were stained with the Klüver-Barrera stain to differentiate neurons from glia, both astrocyt...
Article
Ten pairs of male Long-Evans rats living in nonenriched environments (3 rats per small cage) were transferred to either enriched environments (10 rats per large cage plus "toys") or nonenriched environments (2 rats per small cage) at 766 days of age. One hundred and thirty-eight days later, at 904 days of age, the cerebral cortical thickness from t...
Article
Our results indicate that Long-Evans male rats housed in standard conditions show no significant difference between the areas of sections of their left and right amygdalas. In contrast, the S1 strain maze-bright animals have a significantly greater right amygdala than left. Furthermore, the data indicate an overall increase in mean (R + L)/2 amygda...
Chapter
This chapter deals with the structural changes seen in the brains of aging rats exposed to differential environments. We have previously reviewed the overall progress of experiments from our laboratory indicating brain changes due to modified external stimuli (Diamond and Connor, 1981, 1982). We showed changes in occipital cortical cell number and...
Article
This paper is one of a series presenting right-left differences in the morphology of the rat forebrain, but this presentation differs from the previous ones by offering age-related changes in both sexes. Long-Evans rats were housed with the dam prior to weaning at 21 days of age and three to a cage thereafter. The ages of the animals studied were 6...
Article
In a previous study we reported longer lengths of terminal dendritic segments of superficial pyramidal neurons in the rat visual cortex for neurons from 630-day-old animals that had been exposed to enriched environments. The present investigation extends that finding to the somatosensory cortex.
Article
It has been previously established that the housing condition influences the appearance of the dendritic tree in young animals. The purpose of this investigation was to determine the extent of the influence that the housing condition exerts on morphometric studies involving old animals. Specifically, we found superficial pyramidal cells from the vi...
Article
This report is the fourth in a series on the brains of three groups of male Brattleboro rats. The present study concerns only homozygous Brattleboro rats. One group raised in standard environmental conditions was killed at 60 days of age, another raised in standard conditions was killed at 90 days of age, and a third group raised in standard condit...
Article
The present study determined the effect of the housing condition experienced by old adult male rats on the appearance and number of dendritic spines. Specifically, 20-month-old rats were killed following 6 months of living in either a social environment (three to a cage) or living alone. The total number of dendritic spines per unit length was exam...
Article
Our findings indicate that the hippocampus of the rat varies in structure in the right and left hemispheres and in males and females. A morphologic study of the thickness of the dorsal hippocampus was carried out on celloidin-embedded histologic sections from male, Long-Evans rats of the following ages: 6, 10, 14, 26, 41, 55, 77, 90, 108, 185, 300,...
Article
As a continuation of our previous reports in a series of studies on the brain of Brattleboro rats, the branching of basal dendrites of pyramidal neurons in the upper layers of the occipital cortex was quantified in three groups of male heterozygous and homozygous Brattleboro rats. One group raised in standard environmental conditions was killed at...
Article
Following a series of investigations into the appearance of the basal dendritic skirt of pyramidal cells in the supragranular layers of the occipital cortex of the aged rat, we now extend our findings to the somatosensory cortex of these same animals. Specifically, the total number of dendritic branches increased from 414 to 630 days of age due pri...
Article
The results we have presented indicate that during aging the changes occurring in the different layers are similar in some instances and not in others. The environment does affect the different layers in separate ways. By using only our standard colony environment we learned that there were greater decrease in the cell number per unit area in the l...
Article
Reports of morphologic asymmetry in the mammalian brain are becoming the rule rather than the exception. In a previous publication we noted that in the male Long-Evans rat the right cerebral cortex was generally thicker than the left cortex in all nine areas measured. In the present study, in the majority of cortical areas measured, the right hemis...
Article
Our laboratory reported an increase in the thickness of the occipital cortex in 90-day-old female Long-Evans rats ovariectomized on day 1 compared with sham-operated controls. The present experiment studied the effects of ovariectomy on cerebral cortical synapses. Tissue blocks from the dorsal medial occipital cortex, area 18, of the right hemisphe...
Article
As a sequel to our first report in the series of studies on the brains of Brattleboro rats, measurements in caudal diencephalon, subcortical telencephalon, hippocampus, and pyriform cortex were made in three groups each of male heterozygous and homozygous Brattleboro rats. One group raised in standard conditions was killed at 60 days of age, anothe...
Article
The present investigation was the first to measure the lengths of dendrictic segments from aged animals in different environments to determine if the rates of retraction that occur with age can be influenced by the external environment. Our results show that the sixth-order segments, which represent the segments most distal to the cell body, are 86...
Article
The possible role of the environment in the morphology of the aged brain has been previously discussed in a number of studies. This study used rats which were aged in social rather than in isolated environments. The density of basal dendrites from superficial pyramidal cells from the occipital cortex was analyzed utilizing the concentric circle met...
Article
Changes in cortical thickness were observed in male Brattleboro rats killed at 60 and 90 days of age from standard environmental conditions, and at 90 days of age after 30 days in an enriched condition. When 60- and 90-day-old standard animals were compared, both homozygous Brattleboro rats with diabetes insipidus and also heterozygous nondiabetic...
Article
Our results indicate that specific regions in the right cerebral cortex of the young adult male rat are thicker than the corresponding regions on the left. The differences attain statistical significance in areas 17, 18a, and 39. In contrast, in the young adult female, specific regions in the left cortex are uniformly thicker than the right, though...
Article
The density of dendritic spines was determined by counting spines on 34-μm segments from basal branches of pyramidal cells in layers II and III of the rat occipital cortex. Counts began at the first bifurcation site from the soma, and one segment from each side of the neuron was studied. The results of this investigation indicated a marked decrease...
Article
The response to different environmental conditions and negative air ions was investigated on cerebral cortical serotonin and cyclic nucleotides. The results indicated that negative air ions alter the weight of the cerebral cortex and that concentrations of serotonin and cyclic nucleotides can be altered both by different environments and by negativ...
Article
With the use of Golgi impregnation, this study demonstrated dendritic proliferation in layers II and III in the medial occipital cortex of 444- and 630-day-old male rats. Increases occurred in animals housed in either enriched or standard colony conditions. Specifically, third- and fourth-order basal dendrites increased significantly in frequency f...
Article
Removal of rat ovaries at Day 1 increases cortical thickness by Day 90 when compared with intact littermates (C. Pappas, 1977, Ph.D. Thesis, University of California, Berkeley, Calif.). In the present experiments, using Day 1 sets of sextuplets, one male and one female were gonadectomized; one male and one female were sham-operated; one male and on...
Article
Long—Evans female rats ovariectomized at Day 1 postnatally, and sacrificed at Day 90, developed a thicker cerebral cortex in some regions when compared with sham-ovariectomized littermates (controls). One responsive region, Area 4, was further investigated. A 12% increase in neuron soma size and a 6% increase in neuron nuclear size were found in co...
Article
Fourteen sets of quadruplet, Long-Evans rats were divided accordingly; from each set of quadruplets two were ovariectomized and two were sham-operated at day one. At 21 days of age, the animals were weaned and placed three-four to a cage. At 60 days of age the rats were separated so that one ovariectomized and one sham-operated animal were placed i...
Article
We previously reported changes in the Long-Evans, male rat cerebral cortical thickness as a function of age between birth and 650 days of age [Diamond, M. C., Johnson, R. E., and Ingham, C. (1975). Behav. Biol.14, 163–174]. On the adjacent celloidin-embedded sections from the 26-, 41-, 108-, and 650-day age groups in that study, cell counts and mea...
Article
Light microscopic, histological sections of the forebrain were studied from postnatal developing and aging Long—Evans male rats and from environmentally enriched and impoverished S1 male rats. For the aging study 12 to 16 rats were examined from each of the following groups: 26, 41, 108, and 650 days of age. For the environmental experiments brains...
Article
Pregnant and nonpregnant Long—Evans female rats were placed in enriched, standard colony, and impoverished environmental conditions (comparisons were made among sextuplets). Cerebral cortical depth measurements of the non-pregnant rats supported previous findings that the somesthetic and occipital areas of the environmentally enriched rat are thick...
Article
Cortical depth differences were found between male rats exposed to enriched or impoverished environmental conditions for successively shorter times, i.e., for 15 days (from 25 to 40 days of age), for seven days (25 to 32 days of age), and for four days (26 to 30 or 60 to 64 days of age). If the experiments began at weaning (at 25 days of age), the...
Article
Littermate, S1, male rats were exposed to enriched or impoverished environments for varying periods of time. From photomicrographs of the occipital cortex, neuronal parikarya and neuronal nuclear measurements were taken. In the 25- to 105-day age group, the neuronal nuclear area of the enriched animal was greater than that of the impoverished by 11...
Article
This study was designed to serve as a standard for experiments studying effects of behavior or other variables on the anatomy of the rat brain. The depth of the cerebral cortex, the hippocampus, and the diencephalon were measured, as well as the width of the diencephalon, in male, Long-Evans rats in the following age groups: 6, 10, 14, 20, 26, 41,...
Article
Initial and replication experiments were studied with littermate, S1, male rats 25–55 days of age placed in enriched (EC), standard colony (SC), and impoverished (IC) environments. Measurements of the length of postsynaptic thickenings were taken from asymmeterical axodendritic synapses in layer IV of the dorsal medial occipital cortex. This experi...
Article
To test the persistence of cerebral effects induced by differential experience, littermate rats were placed in an enriched environment (EC) or an impoverished environment (IC) for either 30 or 80 days. Following this initial period, one rat of each litter was transferred from the EC to IC condition while its littermates remained in EC or IC. The se...
Article
Measured the effects of 30 days experience in enriched conditions (EC) or impoverished conditions (IC) on pyramids in the occipital cortex of 40 male Berkeley S1 strain littermate pairs in 4 replication experiments. Using the rapid Golgi method, counts were made of dendritic spines, and the lateral width of basal dendrites was measured. The density...
Article
Examined whether the effects of enriched and impoverished environments on brain chemistry and weights in rats may be mediated hormonally. 3 experiments were done on 78 male Fischer and Long-Evans rats hypophysectomized at about 30 days and on normal controls. Environmental treatments lasted about 35-65 days of age. Among operates as among controls...
Article
Reports a study in which rats placed in enriched or impoverished environments for 4-10 wk. differed in brain anatomy and chemistry. Ss with enriched experience had heavier and thicker cerebral cortexes, greater total activity of acetylcholinesterase but less activity per unit of tissue weight, greater activity of cholinesterase, more glial cells, l...
Article
Notes that hypotheses concerning synaptic changes that might store memory have been appearing ever since E. Tanzi proposed the 1st in 1893. Most have been cast in terms of positive changes with learning, I.e., either growth of new synaptic junctions or changes in size or effectiveness of existing ones. In the last decade, a few theorists have propo...
Article
The first part of this paper deals with rat brain anatomy as affected by variations of starting age and of duration of exposure to enriched (complex) or impoverished (restricted) environmental conditions. Cerebral cortical depth measurements and weights of brain samples are compared. The second part of this report is concerned with an attempt to es...
Chapter
The search for changes in the brain resulting from experience dates back at least two centuries. Only in the last few years, however, has it become clear that environmental variables, including learning and memory, can produce neurochemical and anatomical changes in the brain. In the present volume many of the chapters discuss experiments in which...
Article
The intent of the present research endeavor was to determine the effect of differential environment on some morphological aspects of the immature rat brain. All litters of Long-Evans rats were reduced to three male pups per mother at birth. At six days of age three groups were formed: 1. One mother with her three pups remained in the standard colon...
Article
Histological studies of brains from rats experiencing enriched (EC) or impoverished (IQ environmental conditions were carried out. Cerebral cortical depth measurements, body weights and endocrine organ weights were taken from the following groups of animals: male rats in EC vs. IC, non-pregnant female rats in EC vs. IC, pregnant rats from EC and IC...
Article
Significant differences in size and number of synaptic junctions were found between littcrmate rats assigned at weaning (25 days of age) to enriched or impoverished environments and kept there for 30 days. The synapses measured were asymmetrical axodendritic junctions in the neuropil of layer III of the occipital cortex. Rats given experience in th...
Article
Wet weight of rat cerebral cortex was increased by exposure to an enriched environment, as compared with standard colony or impoverished conditions. Dry weights and wet weights were compared and both yielded identical percentage differences between brains of animals experiencing enrichment and those experiencing impoverishment.
Article
An investigation was carried out to determine the effects of early hypophysectomy (5–6 days of age) and later hypophysectomy (28 days of age) on brain morphology. Graded doses of growth hormone were injected into normal postnatal rats to compare the brain anatomy with that from the early hypophysectomized rats. The animals were divided into five gr...
Article
The development of acetylcholinesterase (AChE) and cholinesterase (ChE) activities, weight measures and protein content were determined for specific brain samples from early hypophysectomized and control female rats at 33–35 days of age. Of the eight brain samples, only two, the somatosensory and ventral cortex, showed significantly less AChE activ...
Article
The morphological development of the rat cerebral cortex was investigated following hypophysectomy at 4–5 days of age. Although the body and endocrineorgan weights of the hypophysectomized rats were much less than those of their littermate controls at 33–35 days of age, the brain weights of the hypophysectomized rats were equal to those of the cont...
Article
Littermate, male, Long-Evans rats were paired, with one of each pair being hypophysectomized at 6 days of age by a surgical parapharyngeal approach. Histological examinations were made of brains from hypophysectomized rats and their intact controls, from hypophysectomized rats injected with 30 μg of thyroxine and their uninjected controls, and from...
Article
This study is another in a series of investigations attempting to define the changes in the brain as a consequence of environmental manipulation. Cortical depth and neuron size measurements were taken on brains of rats from enriched (ECT) and impoverished (IC) environments.Celloidin embedded, 10 μ, transverse sections of formalin fixed rat brains w...
Article
We have previously reported anatomical and chemical changes in the cerebral cortex of rats living in an enriched, stimulating environment. The present study includes additional histological measures such as more extensive depth measures, differential cell counts, and cell size measurements. Celloidin-embedded, thionin-stained sections of the visual...
Article
Rats experiencing an enriched environment develop a heavier, thicker visual cortex than rats living in an isolated condition (Bennett et al., '64). The present experiment was carried out to determine if these enriched-environment animals also possessed a larger neurocranium.Eleven pairs of male littermate rats from the S1 strain were used in Experi...
Article
Changes in brain through experience, demanded by learning theories, are found in experiments with rats.
Article
Rats were raised in a complex environment, receiving daily handling and maze training, while littermate controls were kept in isolation. Compared to controls, the experimental animals had lower specific activity of cholinesterase in the cortex and higher subcortical specific activity, greater weight of cerebal cortex, and greater total cholinestera...

Citations

... As early as 1960, researchers demonstrated that learning and experience could produce profound changes in gross measures of brain morphology in rats such as brain weight and cortical thickness (Krech et al., 1960;Rosenzweig et al., 1972;Klintsova and Greenough, 1999). Subsequently, it has been demonstrated that many aspects of brain structure and function can be modified by learning -including synaptic density, neural and glial cell size and ratio, vascularization, dendritic branching, fMRI activation, and neurotransmitter concentration (Black, et al., 1990;van Praag et al., 2000;Poldrack, 2000;Floyer-Lea et al., 2006). ...
... Overall, the brain findings in the current study are in alignment with prior research indicating that environments enhance cortical complexity [51]. Additionally, previous evidence that wild-caught rats have higher neuronal density in the visual cortex than laboratory-raised control rats reinforces these findings [52]. ...
... Secondly, it has been found that several of the complexity-isolation differences in cerebral weights and enzyme measures tend to be maximal within 15-20 days of differential rearing and diminish when differential rearing is continued beyond this time (Rosenzweig, Bennett, & Diamond, 1967;Diamond et al., 1972). The animals in this study had been reared in their respective conditions for 53 days before the start of testing, which may have been too late to detect differences in their response to cholinergic drugs. ...
... Also, longitudinal testing can control for batch effects and guard against problems associated with a history of exposure to an impoverished environment (Sabolek et al., 2004;Volkers and Scherder, 2011). For example, in cross-sectional studies, cognitive impairment and increased anxiety of the oldest animals arise due to an interaction of age and the length of exposure to social isolation or an impoverished environment (Diamond, 1990;Winocur, 1998;Bell et al., 2009;Diniz et al., 2010;Volkers and Scherder, 2011;Sampedro-Piquero et al., 2014;Sparling et al., 2018;Wang et al., 2018). In contrast, animals that are repeatedly handled and tested across the lifespan exhibit reduced anxiety to novel situations (Dellu et al., 1994;Hall et al., 1997;Febo et al., 2020). ...
... Pioneering research on the effect of environmental enrichment on the brain was conducted by University of California, Berkeley investigators in the 1960s and 1970s (See [3], for a summary). For example, Krech, Rosenzweig and Bennett [4] found that environmental enrichment resulted in an increase in the weight of the visual and somatosensory cortex in rats in comparison to rats kept in isolation (see also [5,6]). More specifically, Diamond et al. [7] found that rats exposed to environmental enrichment had increased cortical thickness, especially in the occipital cortex. ...
... Some of the later studies suggest that further operant involvement in the complex environment may be an essential feature over mere motor activity (Black & Greenough, 1991). Physiologically, more complex environments can increase the complexity of brain (and only brain) RNA, as well as general brain mass and number of synapses, with correlated increases in behavioral capabilities (e.g., Rosenzweig, Krech, Bennett, & Diamond, 1968;Uphouse & Bonner, 1975, also cited in Gottlieb; see Gottlieb,pp. 91,96). ...
... As early as 1960, researchers demonstrated that learning and experience could produce profound changes in gross measures of brain morphology in rats such as brain weight and cortical thickness (Krech et al., 1960; Rosenzweig et al., 1972; Klintsova and Greenough, 1999). Subsequently, it has been demonstrated that many aspects of brain structure and function can be modified by learning — including synaptic density, neural and glial cell size and ratio, vascularization, dendritic branching, fMRI activation, and neurotransmitter concentration (Black, et al., 1990; van Praag et al., 2000; Poldrack, 2000; Floyer-Lea et al., 2006). ...
... Synchronization in the beta-band frequency, however, was observed in the extrastimulated infant at both the first (a) and second testing session (d) the developing neocortical architecture of the brain (Baroncelli et al., 2010;Berardi et al., 2015;Dubois et al., 2006;Johnson, 2001;Paus et al., 2001). A large number of experiments have shown how rodents raised in stimulating environments show an increase in cortical thickness (Bennett et al., 1964;Forgays & Forgays, 1952;Sirevaag et al., 1988). Several studies on experience-dependent changes in the cortex have been using animals like cats and monkeys as well, and in general, these studies have found similar results (e.g., Beaulieu & Colonnier, 1987;Floeter & Greenough, 1979;Stell & Riesen, 1987). ...
... The fundamental hypothesis of enrichment/deprivation research is that 'enrichment' of an animals' environmentor exposure to greater sensory experiences and thus higher information processingimproves learning and memory, while 'deprivation' of species-typical sensory stimuli negatively impacts learning and memory (Greenough, Black & Wallace, 1987;Dukas, 2004). Alternatively, enrichments may counteract the stressors and lack of sensory experiences associated with unnatural 'standard' laboratory conditions and thus allow for exposure to amounts of information typical of a natural environment (Rosenzweig, Bennett & Diamond, 1972;Dukas, 2004;Burghardt, 2013). While these hypotheses say much about the amount (quantity) of information, they say little about the importance of the type (quality) of information (e.g. ...
... The third study measured open-field activity, which has been found to involve both exploratory and emotional components. The Diamond et al. (1980) findings (Table 4) that the right cortex is thicker in areas 17, 18a, 39 is certainly Collins 1977 Glick et al. 1979 Robinson 1979 Severing corpus callosum increased striatal DA asymmetry (rat) Diamond et al. 1980 consistent with these three studies, all of which involve visuospatial perception and orientation, and it suggests possible anatomical sites for the behavioral data. If the localization is correct, lesions in these areas should interfere with or impair these behaviors. ...