thirty adults with parkinson 's disease and 30 neurologically healthy controls individually matched by chronological age ( mean age : 52.03 years , sd = 9.7 ; range from 27 years to 70 years ) , gender ( 19 males and 11 females for both groups , and education ( 6.66% no diploma , 26.6% primary degree,39.9% secondary degree , and 26.66% undergraduate and higher ) participated in this cross - sectional study . the pd patients were selected based on sample availability from neurology clinic of tehran university of medical sciences hospitals and were diagnosed by a neurologist . the severity of the disease for pd group was assessed with the unified parkinson 's disease rating scale ( updrs ) , and ranged from mild to moderate . patients with dementia ( scoring under the recommended cutoff point of 23 on the mmse)(14 ) , patients who were illiterate , and those with other neurological disorders such as cva or history of epilepsy , psychiatric disorder ( depression ) based on medical files and neurologist assessment were excluded . in the current study , verbal fluency test included semantic fluency task and phonemic fluency tasks . onsemantic fluency tasks , participants were asked to name as many animals and fruits as possible . on phonemic tasks , subjects were allowed to generate as many words as possible that began with each of the letters / a/ , /f /and /s/. both tasks were time limited to 60 s of word generation . responses were recorded on an audio tape for later analysis . repeated words or words with similar suffix were not counted . the total verbal fluency score was obtained by counting the total number of words . the independent t - test thirty adults with parkinson 's disease and 30 neurologically healthy controls individually matched by chronological age ( mean age : 52.03 years , sd = 9.7 ; range from 27 years to 70 years ) , gender ( 19 males and 11 females for both groups , and education ( 6.66% no diploma , 26.6% primary degree,39.9% secondary degree , and 26.66% undergraduate and higher ) participated in this cross - sectional study . the pd patients were selected based on sample availability from neurology clinic of tehran university of medical sciences hospitals and were diagnosed by a neurologist . the severity of the disease for pd group was assessed with the unified parkinson 's disease rating scale ( updrs ) , and ranged from mild to moderate . patients with dementia ( scoring under the recommended cutoff point of 23 on the mmse)(14 ) , patients who were illiterate , and those with other neurological disorders such as cva or history of epilepsy , psychiatric disorder ( depression ) based on medical files and neurologist assessment were excluded . in the current study , verbal fluency test included semantic fluency task and phonemic fluency tasks . onsemantic fluency tasks , participants were asked to name as many animals and fruits as possible . on phonemic tasks , subjects were allowed to generate as many words as possible that began with each of the letters / a/ , /f /and /s/. both tasks were time limited to 60 s of word generation . responses were recorded on an audio tape for later analysis . repeated words or words with similar suffix were not counted . for each task , the total numbers of correct words were determined . the total verbal fluency score was obtained by counting the total number of words . the independent t - test the means and standard deviations for letter fluency and semantic fluency were demonstrated in table 1 . overall , participants in both groups generated more words in the semantic fluency task than in the phonemic fluency task . results indicated that normal subjects generated significantly more words in both tasks ( semantic fluency task and letter - fluency task ) than parkinson 's patients ( p < 0.001 ) . semantic , phonemic and verbal fluency performance in parkinson 's disease ( pd ) and normal control ( nc ) subjects a paired t test indicated significance difference between parkinson 's patients and normal subject in total number of words in verbal fluency task ( p < 0.001).table 1 . the main objective of this study was to investigate performance of non - demented pd patients on verbal fluency . our results showed that participants with parkinson 's disease have significant deficits on semantic and phonemic fluency measurement compared to the healthy group . these results are consistent with several previous studies indicating decline in verbal fluency tasks in parkinson 's patients . gurd ( 2000 ) reported parkinson 's patients have difficulty in semantic and phonemic fluency ( 10 ) . however , auriacombe et al . ( 1993 ) found that pd patients did not differ from normal group in phonemic fluency ( 12 ) . in contrast , ivory et al.(3 ) reported no significant difference between pd patients and normal subjects in verbal fluency . 1986 ) found that pd patients generated more words than control group on this task(12 ) . the difference found in results of different studies may be due to the differences in the investigated languages , as the frequencies of words that start with a particular letter vary between languages . 1998 ) reported that spanish subjects produced fewer words than vietnamese participants , and this discrepancy might be due to differences in their languages because animal names in vietnamese are one - syllable words whereas most animal names in spanish are multisyllabic(15 ) . the results of the present study that pd demonstrate deficit in verbal fluency could be viewed as consistent with language impairment in pd . crosson ( 1985 ) reported that basal ganglia damage could affect language formulation by their connections with the cortex(5 ) . verbal fluency not only evaluates semantic and phoneme knowledge of lexical memory by searching specifics emanticor phonemes class , but subjects should also be able to track previous responses and prevent activation of other categories by executive skills . therefore , verbal fluency deficit in pd patients undoubtedly represents executive dysfunction . higginson et al ( 2003 ) reported that working memory and verbal fluency correlated with executive functions ( 16 ) . ( 1992 ) have also suggested that poor performance in semantic fluency in these patients is associated with a specific deficit in semantic memory , whilst raskin et al . ( 2009 ) suggested that this problem is caused by a deficit in semantic retrieval and the ability to register , store intact(17 , 18 ) . ( 2012 ) reported that basal ganglia structures are associated with verbal fluency ( 19 ) . however , a number of neuroimaging studies reported that left prefrontal cortex and subcortical regions correlate with verbal fluency ( 20 , 21 ) . on the other hand , there is much evidence of frontal dysfunction in parkinson patients ( 17 ) . based on this reasoning , further studies are needed to investigate a possible relation between verbal fluency deficits with subcortical lesions in pd . in summary assessing language and executive function by verbal fluency test and early intervention may be effective . conclusion a high proportion of patients with mde also had a sub threshold hypomania or mania . findings suggest that bipolar features are more frequent than symptoms indicated by dsm - iv - tr , and exclusion criteria of mood disorders in this classification should be revised . dsm - iv classification appears to be too narrow or rigid to distinguish amore subtle and  softer  form of bipolar cases from pure unipolar cases . first , we did not assess the possible age - related changes in the cognitive and language abilities in our patients , although the previous research reported that aging does not affect the phonemic fluency . second limitation of the present study was that we were unable to match patients for duration and the time course of their disease , although we attempted to control the severity of parkinson in patients group according to unified parkinson 's disease rating scale . future efforts will be directed toward investigation of the time course of change in verbal fluency performance in pd . the present study revealsa significant deficit in non - demented pd that supports findings from previous studies . the deficit in verbal fluency in pd might be associated with cognitive impairment ( executive and memory ) and complex language disorders in pd . furthermore , a recent cross - sectional study on a small group of pd patients demonstrated that tests of memory , language processing and cognitive function are important in early stage in this group . neuropsychologists and speech  language pathologists now routinely assess language and cognitive abilities of pd , and the data presented here illustrates the importance of developing neuropsychological instruments that are sensitive to cognitive deficit . finally , further research using functional brain imaging during verbal fluency tasks is necessary to evaluate the pathology underlying the verbal fluency deficit in pd .