The Negativity Biases Of Depression And Its Neuro Machanism

The case rate and recurrence rate of depression is very high so that it has become a main public health issues;and the reasons leading to depression remain unclear.Recently factors such as cognition characteristics,attribution style,and personality were considered candidates causing depression,among which negativity attentional biases fascinated much studies.Negativity attentional bias is a phenomenon that individuals give more processions to negative stimuli.And the inhibition of return paradigm is often employed to probe the negativity attentional biases of individuals.Studies concerning depression individuals and negativity attentional biases are immature and have four problems.First,there are few studies focusing on the negativity attentional biases of the depressions’,although so many studies have investigated the negativity biases of the depressions’.Second,the specificity of the depressions’ attentional biases deserving further studies.The previous studies indicated that not all negative stimuli induce attentional biases: some stimuli related with anxiety and self esteem can not induce attentional biases;but some related with depression or sad faces can induce the attentional biases of depression patients.Third,the effect of emotion arousal on depression needs more attention.The previous studies mainly explored the effects of emotional valence,of which none took the arousal of independent factors causing depression.Fourth,the relationship between depression and neurochemical materials remains unknown.Although some studies explored the neuro activities of depression through fMRI or ERPs techniques,it lacks direct evidence to judge effect of neuroactivities.Against the limits of previous studies,the present dissertation tried to explore the negativity attentional biases of the depression using inhibition of return cue-target paradigm,and to detect the causal relationship between attentional biases and neurochemical materials.The present dissertation includes five studies and tried to answer the following five questions,(1)compared to the control group,does the experimental group have inhibition of return;(2)does the experimental group have negativity attentional biases;(3)does the attentional biases be related with negative depression stimuli;(4)does theattentional biases be mediated by the emotional arousal;(5)is there causal relationship between depression and neurotransmitter.The study one detected the inhibition of return effects using neutral stimuli.The results of a factor-experiments suggested that the control group has inhibition of return effect under the three time duration conditions,but the depression group only have inhibition of return effect under the condition of 14 ms.Study two used three types of stimuli including neutral,happy and sad face pictures to detect the negativity biases of the depressed.The results indicated that both the experimental group and control group generated negativity biases under the neutral and happy faces conditions.The control group produced inhibition of return effect under three types of SOA conditions(i.e.SOA=14ms,250 ms,and 750ms);the experimental group not didn’t generated any inhibition of return effect,but generated a cue effect under condition of SOA=250 ms meaning the depressed appeared negativity biases.Study three employed sad,anger and fear face pictures as cues to probe whether the negativity biases are related with negative emotions.The results suggested that(1)for the sad pictures the control group generated the inhibition of return effect under all SOA conditions,while the experimental group didn’t produce any inhibition of return effect,but the cue effects.(2)For fear face pictures,the control group generated the inhibition of return effect under SOA=14 ms and SOA=750 ms,while the experimental group didn’t produce any inhibition of return effect.(3)For the anger picture stimuli,both the experimental group and control group didn’t generate any inhibition of return effect.These results suggested that the attentional biases of depressed individual were specific for some type of emotion.Study four studied the mediating effect of emotion arousal on the attentional biases of depression participants using high level and low level arousal sad pictures as stimuli.The results indicated that:(1)for the high arousal stimuli,the control group only generated inhibition of return effect under the condition of SOA =14 ms;the experimental group didn’t produce any inhibition of return effect.(2)for the low arousal stimuli,the control group generated inhibition of return effect under three SOA conditions(i.e.SOA=14 ms,250 ms,and 750 ms);while the experimental group only produced inhibition of return effect under condition of SOA=14 ms.These results indicated that the mediating effect of emotion arousal is significant.Study five tested the relationship between neurotransmitter and negativity biases using the self-developed depression rat model.The results indicated that(1)the depression model was developed successfully,and the experimental group appeareddepression behaviors according to the change of weight,taking food,and coats of rats;(2)the experimental group had significant higher level of 5-HIAA and DOPAC;while had significant lower level of 5-HT,EP and HVA;(3)for the control group rats,the level of 5-HIAA,DOPAC and HVA is correlated significantly with their response time and correctness rate;while for the experimental group rats,the only 5-HIAA and DOPAC have significant correlation with their response time and correctness rate.In sum,the present dissertation found that the negativity attentional biases exist in depression individuals which produced under specific negative emotion type.And also found that the effect of negativity attentional biases were mediated by the emotion arousal and correlated with the neurotransmitter level.These results supported the Beck’s cognition model which provides a new direction and evidence of studying the negativity biases of depression.