A retrospective survey of human hydatidosis based on hospital records during the period of 10 years

Hydatid cyst is a parasitic infection that is widely seen endemically in the Middle East countries. We studied hydatid cyst pattern in hospitalized adult patients in our hospital from 2000 to 2010. In this study 89 patients, 50 females and 39 males who were diagnosed to have hydatid cyst were evaluated. The mean age of the patients was 37.3 and the mean hospital stay was 10.1 days. The main complaint was abdominal pain (66.2%). The most common localization of cysts was the liver and the most radiological method to diagnose the disease was ultrasonography followed by CT scan. Our recurrence rate was more than average. We had no mortality and did not find any serious postoperative complication. Safe surgery is a role for hydatid cysts.

Color improves speed of processing but not perception in a motion illusion

When two superimposed surfaces of dots move in different directions, the perceived directions are shifted away from each other. This perceptual illusion has been termed direction repulsion and is thought to be due to mutual inhibition between the representations of the two directions. It has further been shown that a speed difference between the two surfaces attenuates direction repulsion. As speed and direction are both necessary components of representing motion, the reduction in direction repulsion can be attributed to the additional motion information strengthening the representations of the two directions and thus reducing the mutual inhibition. We tested whether bottom-up attention and top-down task demands, in the form of color differences between the two surfaces, would also enhance motion processing, reducing direction repulsion. We found that the addition of color differences did not improve direction discrimination and reduce direction repulsion. However, we did find that adding a color difference improved performance on the task. We hypothesized that the performance differences were due to the limited presentation time of the stimuli. We tested this in a follow-up experiment where we varied the time of presentation to determine the duration needed to successfully perform the task with and without the color difference. As we expected, color segmentation reduced the amount of time needed to process and encode both directions of motion. Thus we find a dissociation between the effects of attention on the speed of processing and conscious perception of direction. We propose four potential mechanisms wherein color speeds figure-ground segmentation of an object, attentional switching between objects, direction discrimination and/or the accumulation of motion information for decision-making, without affecting conscious perception of the direction. Potential neural bases are also explored.

Prevalence of Trichomonas vaginalis Infection in Hamadan City, Western Iran

BACKGROUND

Infection with Trichomonas vaginalis is one of the most common sexually transmitted diseases (STDs) in humans. The prevalence of infection in Iran has been reported between 2 to 8%, depending on deferent socio-cultural conditions. This study aimed to determine the prevalence of T. vaginalis in women referred to gynecologic clinics in Hamadan city, West of Iran.

METHODS

This descriptive cross-sectional study was conducted on 750 women who referred to Gynecologic clinics in Hamadan from November 2010 to July 2011. Vaginal samples were obtained from them and examined by wet mount and culture methods for the detection of T. vaginalis.

RESULTS

Sixteen out of 750 vaginal swab specimens (2.1%) were culture positive for T. vaginalis and 13 of these positive specimens (1.7%) were wet mount positive. Only 12 of 42 patients who were clinically diagnosed as having T. vaginalis infection, confirmed by culture method. Five hundred and fifty of the participants women (73.3%) had at least one of signs and symptoms of trichomoniasis. No statistical correlation was observed between clinical manifestations and parasitological results (p>0.05).

CONCLUSION

This study showed low prevalence of T. vaginalis infection in the study population. Since clinical signs of trichomonal vaginitis are the same of other STDs, a confirmatory laboratory diagnosis is necessary. Wet smear as well as culture are sensitive for detection of T. vaginalis.

Risk factor investigation for cardiovascular health through WHO STEPS approach in Ardabil, Iran

Objectives:

Reliable evidence is the keystone for any noncommunicable disease (NCD) prevention plan to be initiated. In this study we carried out a risk factor investigation based on the WHO Stepwise approach to Surveillance (STEPS).

Methods:

The study was conducted on 1000 adults between 15 and 64 years of age living in Ardabil province, north-west Iran during 2006, based on the WHO STEPS approach to surveillance of risk factors for NCD. At this stage only the first and second steps were carried out. Data were collected through standard questionnaires and methods analyzed using STATA version 8 statistical software package.

Results:

29.0% of men and 2.6% of women were current daily tobacco smokers. The mean number of manufactured cigarettes smoked per day was 18.9 among current daily smokers. Smoking was most prevalent among men of low-income families and those of lower education. The mean body mass index (BMI) was 26.6 kg/m², and was significantly correlated with systolic blood pressure. 58.9% were overweight or obese; 18.0% had raised blood pressure and 3.7% had isolated systolic hypertension. The mean number of servings of fruit consumed per day was 1.1; 33.1% had low levels of activity. Combined risk factor analysis showed that 4.1% of participants were in the low-risk group (up to 5.1% among men and 3.2% among women). Those in the high-risk group comprised 25.6% in the 25- to 44-year age group and 49.7% in the 45- to 64-year age group. Mean BMI increased by age in both sexes at least at the first three decades of adult life.

Conclusion:

Based on observed status of risk for cardiovascular health, burden of cardiovascular diseases is expected to increase if an effective prevention strategy is not undertaken.

Nervous system tumors in adult immigrants to Sweden by subsite and histology

BACKGROUND

The coding of histology of nervous system (NS) tumors with various degrees of malignancies differs between cancer registries, whereby the comparison of incidence rates from one registry to another seems difficult. No study has systematically defined whether the change in the risk of NS tumors upon immigration in adulthood varies by subsite or histology. Therefore, we aimed to address this issue amongst the first-generation immigrants to Sweden based on a large uniform cancer registry data (1958-2006).

METHODS

The nationwide Swedish Family-Cancer Database (2008 version; >11.8 million individuals; 1.8 million immigrants; histology code in force since 1958) was used to calculate standardized incidence ratios (SIRs). We analyzed 28,981 adult cases of NS tumors amongst Swedes and 2519 amongst immigrants (age ≥ 30).

RESULTS

Significantly decreased risks for brain glioma were amongst German (SIR = 0.64), Eastern European (0.62), some Asian (0.71), Chilean (0.34), and African immigrants (0.52). We found an increased risk for brain meningioma amongst Finns (1.15) and former Yugoslavians (1.33), whilst only Norwegians (0.71) and Latin Americans (0.21) had a decreased risk. The risk for spinal ependymoma and astrocytoma was increased in Germans (3.66) and former Yugoslavians (8.89). We found no significant difference for peripheral nerve tumors between immigrants and the native Swedes.

CONCLUSION

Significant differences between risk of NS tumors amongst immigrants and the native Swedes may suggest different risk factor profiles for glioma compared to meningioma indicating a higher etiological role of genetic background or childhood environmental risk factors rather than exposures after immigration.

Idiopathic generalized epilepsies: a follow-up study in a single-center

OBJECTIVE

To characterize adult patients with idiopathic generalized epilepsies (IGEs) with precise evaluation and to assess factors related to refractoriness.

MATERIALS AND METHODS

Hospital records of all our patients with IGEs (n = 128) were evaluated in 2005 and followed-up until 2008.

RESULTS

In 2005, 76% of patients were 1-year seizure-free. Seizure freedom increased to 82% during the 3-year follow-up. Seizure freedom was not significantly associated with age, age at diagnosis, epilepsy duration, exposure to inappropriate initial antiepileptic drug (AED), or delay time between starting initial AED and appropriate AED. Women constituted 78% of patients with merely provoked seizures. In 58% of women with recent seizure, one to two avoidable precipitating factors, such as lack of sleep, alcohol, and forgetting to take AED, were observed. In 2008, all patients with no medication, 91% of monotherapy patients, 60% of patients on two AED, and 14% of patients on three AED were seizure-free.

CONCLUSIONS

Most of patients with IGEs can be successfully treated with monotherapy. Refractory seizures in some patients may be because of avoidable factors, especially in young women.

CD 28 gene polymorphism and plasma concentration of soluble CD 28 in Iranian patients with visceral leishmaniasis

In visceral leishmaniasis (VL), the development of protective immunity is associated with expansion of leishmania-specific T-cell responses. Because of the essential role of CD28 in the effectiveness of T-cell activation, this study was carried out to investigate the CD28 gene polymorphism and plasma levels of soluble (s) CD28 molecule in Iranian patients with VL. Plasma concentrations of CD28 in 88 patients with VL, 132 individual with subclinical leishmaniasis, and 100 seronegative healthy controls were measured by enzyme-linked immunosorbent assay. Genotyping of CD28 gene polymorphism was performed by polymerase chain reaction based allotyping method using allele-specific primers for C or T at intron 3 position +17 in three groups. The frequency of CC genotype was significantly higher in subclinical VL patients (42.4%) than active VL group (27.3%) and healthy controls (16%) (P<0.001). Also, the frequency of allele C among subclinical VL group (57.6%) was significantly higher than active VL (40.9%) and control groups (34%) (p=0.003). No significant differences were observed between the plasma levels of sCD28 in three groups. Our findings suggest that the CD28 gene may have significant role in the protection of active VL in the Iranian population.

A color hierarchy for automatic target selection

Visual processing of color starts at the cones in the retina and continues through ventral stream visual areas, called the parvocellular pathway. Motion processing also starts in the retina but continues through dorsal stream visual areas, called the magnocellular system. Color and motion processing are functionally and anatomically discrete. Previously, motion processing areas MT and MST have been shown to have no color selectivity to a moving stimulus; the neurons were colorblind whenever color was presented along with motion. This occurs when the stimuli are luminance-defined versus the background and is considered achromatic motion processing. Is motion processing independent of color processing? We find that motion processing is intrinsically modulated by color. Color modulated smooth pursuit eye movements produced upon saccading to an aperture containing a surface of coherently moving dots upon a black background. Furthermore, when two surfaces that differed in color were present, one surface was automatically selected based upon a color hierarchy. The strength of that selection depended upon the distance between the two colors in color space. A quantifiable color hierarchy for automatic target selection has wide-ranging implications from sports to advertising to human-computer interfaces.

Gene polymorphism in transforming growth factor-beta codon 10 is associated with susceptibility to Giardiasis

Secretory immunoglobulin A (S-IgA) antibodies have a central role in anti-Giardial defence. It has been demonstrated that transforming growth factor-beta1 (TGF-beta1) stimulates B lymphocytes to produce and secrete S-IgA. We sought to determine the association between TGF-beta1 polymorphism (T+869C) with susceptibility to Giardiasis. The TGF-beta1 genotypes and levels of salivary (S-IgA) were analysed in individuals with Giardiasis (97 symptomatic and 57 asymptomatic) and controls (n = 92). Individuals with symptomatic Giardiasis had the lowest levels of S-IgA compared to individuals in asymptomatic Giardiasis and control groups (97%, 73% and 43%, <1 g L(-1), respectively, P = 0.002). The frequency of allele C and CC genotypes of TGF-beta1 polymorphism was significantly higher among symptomatic patients than asymptomatic and control groups. Logistic regression analysis demonstrated that the individuals homozygous for allele C of TGF-beta1 had a significantly higher risk for symptomatic Giardiasis with odds ratio of 2.76 (95% CI: 3.88, 1.71, P = 0.007). Among the participants with TT genotype per cent of individuals with S-IgA level of more than 1 g L(-1) was almost twice the percentage in CC genotype individuals (14% versus 7% respectively P = 0.01). Our data suggest that CC genotype of TGF-beta1 polymorphism at codon 10 is associated with occurrence of Giardiasis.

Retention rates of new antiepileptic drugs in localization-related epilepsy: a single-center study

OBJECTIVES

We evaluated long-term retention rates of newer antiepileptic drugs (AED) in adults with localization-related epilepsy retrospectively.

METHODS

We estimated retention rates by Kaplan-Meier method in all 222 patients (age > or = 16) with localization-related epilepsy exposed to new AED at the Tampere University Hospital.

RESULTS

There were 141 patients exposed to lamotrigine, 78 to levetiracetam, 97 to topiramate, 68 to gabapentin, and 69 to tiagabine. Three-year retention rate for lamotrigine was 73.5%, levetiracetam 65.4%, topiramate 64.2%, gabapentin 41.7%, and tiagabine 38.2%. The most common cause for withdrawal of these AED was lack of efficacy.

CONCLUSIONS

Our study suggests that there are clinically significant differences among gabapentin, lamotrigine, levetiracetam, tiagabine, and topiramate as treatment for focal epilepsy in everyday practice. Gabapentin and tiagabine seem to be less useful than the other three AED. Furthermore, our study supports the value of retention rate studies in assessing outcome of the drugs in clinical practice.

Interacting competitive selection in attention and binocular rivalry

Visuomotor processing is selective - only a small subset of stimuli that impinge on the retinae reach perceptual awareness and/or elicit behavioral responses. Both binocular rivalry and attention involve visual selection, but affect perception quite differently. During rivalry, awareness alternates between different stimuli presented to the two eyes. In contrast, attending to one of the two stimuli impairs discrimination of the ignored stimulus, but without causing it to perceptually disappear. We review experiments demonstrating that, despite their phenomenological differences, attention and rivalry depend upon shared competitive selection mechanisms. These experiments, moreover, reveal stimulus selection that is surface-based and requires coordination between the different neuronal populations that respond as a surface changes its attributes (type of motion) over time. This surface-based selection, in turn biases interocular competition, favoring the eye whose image is consistent with the selected surface. The review ends with speculation about the role of the thalamus in mediating this dynamic coordination, as well as thoughts about what underlies the differences in the phenomenology of selective attention and rivalry.

Clinical predictors in patients with refractory epilepsy exposed to levetiracetam: a single-center study

OBJECTIVES

This aim of the study was to ascertain the importance of clinical parameters on the response to treatment in refractory epilepsy patients on levetiracetam (LEV).

MATERIALS AND METHODS

We retrospectively evaluated medical records of 132 patients aged 17-78 years with refractory epilepsy (defined as a failure of at least two antiepileptic drugs due to the lack of efficacy) exposed to LEV. We analyzed the response (seizure freedom or continuing LEV) using logistic regression.

RESULTS

Of 132 patients exposed to LEV, 103 cases continued the drug. Of the discontinuations (29/132), 75% were for lack of efficacy and 25% for tolerability problems. Twenty-three percent of the previously refractory patients achieved seizure freedom for at least 1 year with LEV in combination therapy. The dose of LEV in 80% of seizure-free patients was 1000 mg/day or less. The duration of epilepsy, age and sex were not associated with response to LEV. Seizure freedom was associated with epileptic syndrome or etiology. If no specific syndrome was recognized, there was a significantly greater chance for response compared with temporal lobe epilepsy (OR 20.76; 95% CI 2.12-203.61).

CONCLUSIONS

Our study was based on the careful clinical evaluation of the patients with extensive use of video EEG (50%) and MRI scans (95%). These clinical predictors were evasive in previous studies. This study showed that they are worth pursuing but significantly larger groups of patients need to be investigated to reach significant findings.

Seroepidemiology of toxoplasmosis in primigravida women in Hamadan, Islamic Republic of Iran, 2004

We determined the prevalence of Toxoplasma antibodies in 576 primigravid women randomly selected from health houses in Hamadan. The relationship between positivity and some risk factors was assessed. Data were collected by questionnaire and blood samples examined for Toxoplasma antibodies by indirect fluorescent antibody test. Of the 576 women, 193 (33.5%) were positive for Toxoplasma antibodies (titre > or = 1:20). Age, consumption of fresh undercooked meat and frequent consumption of raw vegetables were statistically significantly associated with higher infection rates. Educational level, touching cats, handling raw meat, farming, method of washing vegetables and consumption of raw milk and eggs were not associated with infection.

A Study on the Prevalence of Cryptosporidium in HIV Positive Patients

BACKGROUND

AIDS is acquired by infection with HIV (human immuno-deficiency virus). It leaves the host susceptible to malignant and unusual infections especially opportunistic ones. Most of AIDS patients infected with opportunistic parasitic infections die because of chronic diarrhea and deaths due to Cryptosporidium diarrhea in AIDS patients are considerable in the recent two decades. The aim of this study is to find Cryptosporidium parasite in AIDS patients referring to the center of Diseases consultation in Kermanshah province and to determine the frequency of infection in those patients.

METHODS

In this study stool and blood samples were collected from 75 AIDS patients referring regularly to the Center of Diseases Consultation in Kermanshah and the gathered information were filled in the questionnaires together with their personal information regarding their names, sex and etc. Stool samples were tested using direct and formalin ether methods and then the smears that were dyed using modified acid fast staining were examined. Peripheral blood samples were used to determine the CD4 counts.

RESULTS

The results showed that the frequency of infection with Cryptosporidium in AIDS patients was 26.7% (20 cases).

CONCLUSION

According to the study, as the number of CD4 decreased in the patients, the probability of infection with opportunistic parasites increased and increase in the number CD4 that is normally accompanied with strengthening the body immune system resulted in the decrease in the frequency of infection with Cryptosporidium.

Stimulus-specific competitive selection in macaque extrastriate visual area V4

Macaque visual area V4 has been implicated in the selective processing of stimuli. Prior studies of selection in area V4 have used spatially separate stimuli, thus confounding selection of retinotopic location with selection of the stimulus at that location. We asked whether V4 neurons can selectively respond to one of two differently colored stimuli even when they are spatially superimposed. We find that delaying one of the two stimuli leads to selective processing of the delayed stimulus by area V4 neurons. This selective processing persists when the stimuli move together across the visual field, thereby successively activating different populations of neurons. We also find that this effect is not a spatially global form of feature-based selection. We conclude that selective processing in area V4 is neither exclusively spatial nor feature-based and may thus be surface- or object-based.

Temporal resolution for the perception of features and conjunctions

The visual system decomposes stimuli into their constituent features, represented by neurons with different feature selectivities. How the signals carried by these feature-selective neurons are integrated into coherent object representations is unknown. To constrain the set of possible integrative mechanisms, we quantified the temporal resolution of perception for color, orientation, and conjunctions of these two features. We find that temporal resolution is measurably higher for each feature than for their conjunction, indicating that time is required to integrate features into a perceptual whole. This finding places temporal limits on the mechanisms that could mediate this form of perceptual integration.

Adaptation of gender derived from biological motion

Human observers adapted to complex biological motions that distinguish males from females: viewing the gait of one gender biased judgments of subsequent gaits toward the opposite gender. This adaptation was not simply due to local features of the stimuli but instead relied upon the global motion of the figures. These results suggest the existence of neurons selective for gender and demonstrate that gender-from-motion judgments are not fixed but depend upon recent viewing history.

A Motion-Dependent Distortion of Retinotopy in Area V4

When one element in an apparent motion sequence differs in color from the others, it is perceived as shifted along the motion trajectory. We examined whether V4 neurons encode the physical or perceived location of this "flashed" element by recording neuronal responses while monkeys viewed these stimuli. The retinotopic locus of V4 activity evoked by the flashed element shifted along the motion trajectory. The magnitude of the shift is consistent with the perceptual shift in humans viewing identical stimuli. This retinotopic distortion depended on the presence of a flashed element but was observed for both color-selective and non-color-selective neurons. The distortion was undiminished when the flashed element terminated the sequence, a condition that reduced the perceptual shift in humans. These findings are consistent with a Bayesian model of localization in which perceived location is derived from position signals optimally integrated across visual areas.

Visuomotor origins of covert spatial attention

Covert spatial attention produces biases in perceptual performance and neural processing of behaviorally relevant stimuli in the absence of overt orienting movements. The neural mechanism that gives rise to these effects is poorly understood. This paper surveys past evidence of a relationship between oculomotor control and visual spatial attention and more recent evidence of a causal link between the control of saccadic eye movements by frontal cortex and covert visual selection. Both suggest that the mechanism of covert spatial attention emerges as a consequence of the reciprocal interactions between neural circuits primarily involved in specifying the visual properties of potential targets and those involved in specifying the movements needed to fixate them.

Microstimulation of the frontal eye field and its effects on covert spatial attention

Many studies have established that the strength of visual perception and the strength of visual representations within visual cortex vary according to the focus of covert spatial attention. While it is clear that attention can modulate visual signals, the source of this modulation remains unknown. We have examined the possibility that saccade related mechanisms provide a source of spatial attention by studying the effects of electrical microstimulation of the frontal eye fields (FEF) on spatial attention. Monkeys performed a task in which they had to detect luminance changes of a peripheral target while ignoring a flashing distracter. The target luminance change could be preceded by stimulation of the FEF at current levels below that which evoked saccadic eye movements. We found that when the target change was preceded by stimulation of FEF, the monkey could detect smaller changes in target luminance. The increased sensitivity to the target change only occurred when the target was placed in the part of the visual field represented by neurons at the stimulation site. The magnitude of improvement depended on the temporal asynchrony of the stimulation onset and the target event. No significant effect of stimulation was observed when long intervals (>300 ms) between stimulation and the target event were used, and the magnitude of the increased sensitivity decreased systematically with increasing asynchrony. At the shortest asynchrony, FEF stimulation temporally overlapped the target event and the magnitude of the improvement was comparable to that of removing the distracter from the task. These results demonstrate that transient, but potent improvements in the deployment of covert spatial attention can be obtained by microstimulation of FEF sites from which saccadic eye movements are also evoked.

Attentional selection of superimposed surfaces cannot be explained by modulation of the gain of color channels

When two differently colored, superimposed patterns of dots rotate in opposite directions, this yields the percept of two superimposed transparent surfaces. If observers are cued to attend to one set of dots, they are impaired in making judgments about the other set. Since the two sets of dots are overlapping, the cueing effect cannot be explained by spatial attention. This has led to the interpretation that the impairment reflects surface-based attentional selection. However, recent single-unit recording studies in monkeys have found that attention can modulate the gain of neurons tuned for features such as color. Thus, rather than reflecting the selection of a surface, the behavioral effects might simply reflect a reduction in the gain of color channels selective for the color of the uncued set of dots (feature-based attention), as if viewing the surfaces through a colored filter. If so, then the impairment should be eliminated when the two surfaces are made the same color. Instead, we find that the impairment persists with no reduction in strength. Our findings thus rule out the color gain explanation.

Response latencies of neurons in visual areas MT and MST of monkeys with striate cortex lesions

Cortical area, MT (middle temporal area) is specialized for the visual analysis of stimulus motion in the brain. It has been suggested [Brain 118 (1995) 1375] that motion signals reach area MT via two dissociable routes, namely a 'direct' route which bypasses primary visual cortex (area, striate cortex (V1)) and is specialized for processing 'fast' motion (defined as faster than 6 degrees/s) with a relatively short latency, and an 'indirect' route via area V1 for processing 'slow' motion (slower than 6 degrees/s) with a relatively long latency. We tested this proposal by measuring the effects of unilateral V1 lesions on the magnitudes and latencies of responses to fast- and slow-motion (depicted by random dot kinematograms (RDK) ) of single neurons in areas MT and medial superior temporal area (MST) of anaesthetized macaque monkeys. In the unlesioned hemisphere contralateral to a V1 lesion, response magnitudes and latencies of MT neurons were similar to those previously reported from MT neurons in normal monkeys, and there was no significant association between slow movement and long response latency (>100 ms), or between fast movement and short latency (< or =100 ms). V1 lesions led to diminished response magnitudes and increased latencies in area MT of the lesioned hemisphere, but did not selectively abolish MT responses to slow moving stimuli, or abolish long-latency responses to either slow- or fast-moving stimuli. Response magnitudes and latencies in area MST, which receives visual inputs directly from area MT and is also specialized for visual analysis of motion, were unaffected by V1 lesions (though we have shown elsewhere that directionally-selective responses in both areas were impaired by V1 lesions). Overall, the results are incompatible with the hypothesis that there are dissociable routes to MT specialized for processing separately fast and slow motion.

Attention! V1 neurons lining up for inspection

In this issue of Neuron, Roelfsema and Spekreijse report that macaque V1 neuron responses are correlated with target choice in a task requiring monkeys to attentively trace a line to plan a saccade. These results provide evidence that V1 is actively involved in the interpretation of visual stimuli.

Control of eye movements and spatial attention

Several lines of evidence suggest that planning eye movements and directing visuospatial attention share overlapping brain mechanisms. This study tested whether spatial attention can be enhanced by altering oculomotor signals within the brain. Monkeys performed a spatial attention task while neurons within the frontal eye field, an oculomotor area within prefrontal cortex, were electrically stimulated below the level at which eye movements are evoked. We found that we could improve the monkey's performance with microstimulation when, but only when, the object to be attended was positioned in the space represented by the cortical stimulation site.

Hippocampal neurogenesis in adult Old World primates

The production of new hippocampal neurons in adulthood has been well documented in rodents. Recent studies have extended these findings to other mammalian species, such as tree shrews and marmoset monkeys. However, hippocampal neurogenesis has not been demonstrated in adult Old World primates. To investigate this possibility, we injected 11 adult Old World monkeys of different ages (5-23 years) with the thymidine analog bromodeoxyuridine and examined the fate of the labeled cells at different survival times by using neuronal and glial markers. In the young-adult and middle-aged monkeys, we found a substantial number of cells that incorporated bromodeoxyuridine and exhibited morphological and biochemical characteristics of immature and mature neurons. New cells located in the dentate gyrus expressed a marker of immature granule neurons, Turned On After Division 64 kDa protein, as well as markers of mature granule neurons including neuron specific enolase, neuronal nuclei, and the calcium-binding protein calbindin. Fewer new cells expressed the astroglial marker glial fibrillary acidic protein. Evidence of neurogenesis was observed in the oldest monkeys (23 years) as well, but it appeared to be less robust. These results indicate that the adult brains of Old World monkeys produce new hippocampal neurons. Adult macaque monkeys may provide a useful primate model for studying the functional significance of adult neurogenesis.