Functional near-infrared spectroscopy in elderly patients with four types of dementia

BACKGROUND

Functional near-infrared spectroscopy (fNIRS) is commonly used to study human brain function by measuring the hemodynamic signals originating from cortical activation and provides a new noninvasive detection method for identifying dementia.

AIM

To investigate the fNIRS imaging technique and its clinical application in differential diagnosis of subtype dementias including frontotemporal lobe dementia, Lewy body dementia, Parkinson’s disease dementia (PDD) and Alzheimer’s disease (AD).

METHODS

Four patients with different types of dementia were examined with fNIRS during two tasks and a resting state. We adopted the verbal fluency task, working memory task and resting state task. Each patient was compared on the same task. We conducted and analyzed the fNIRS data using a general linear model and Pearson’s correlation analysis.

RESULTS

Compared with other types of dementias, fNIRS showed the left frontotemporal and prefrontal lobes to be poorly activated during the verbal fluency task in frontotemporal dementia. In Lewy body dementia, severe asymmetry of prefrontal lobes appeared during both verbal fluency and working memory tasks, and the patient had low functional connectivity during a resting state. In PDD, the patient’s prefrontal cortex showed lower excitability than the temporal lobe during the verbal fluency task, while the prefrontal cortex showed higher excitability during the working memory task. The patient with AD showed poor prefrontal and temporal activation during the working memory task, and more activation of frontopolar instead of the dorsolateral prefrontal cortex.

CONCLUSION

Different hemodynamic characteristics of four types of dementia (as seen by fNIRS imaging) provides evidence that fNIRS can serve as a potential tool for the diagnosis between dementia subtypes.

Roles of central interleukin-1 on stress-induced-hypertension and footshock-induced-analgesia in rats

Central interleukin-1 (IL-1) plays an important role in mediating the neural, endocrine, and behavioral responses to stressors. Here we tested whether central IL-1 is involved in stress-induced hypertension or footshock (FS)-induced-analgesia. We observed that: (1) intracerebral ventricular injection of (ICV) IL-1beta induced pressor responses; (2) hypertension induced by IL-1beta was blocked by ICV an IL-1 antagonist, IL-1ra; (3) ICV IL-1ra attenuated the pressor response induced by FS but intravenous injection of IL-1ra did not significantly reduce this response; (4) the hypertensive response to conditioned fear stimuli was reversed by ICV IL-1ra; (5) FS-induced-analgesia was attenuated by ICV IL-1ra and this effect disappeared 15 min after ICV IL-1ra. These results suggest that both the pressor response to FS or conditioned fear stimuli and short lasting analgesia induced by FS are mediated by central IL-1.

The central mechanism of the depressor-bradycardia effect of "Tinggong

Roles of central adrenergic receptors and opioid receptors in the depressor-bradycardia effect of 3V, 2Hz "Tinggong-Quchi" electroacupuncture (the EA-DpB, i.e.the depressor bradycardia induced by electroacupuncture) were studied by intracerebroventricula (icv) injection of prazosin, yohimbine or propanol, naloxone or by intra-arachnoid (ith) injection of naloxone. Voltage-dependent depressor effects were induced by 2Hz "Tinggong-Quchi" acupuncture. The depressor effect of 3V, 2Hz " Tinggong-Quchi " acupuncture was attenuated by icv injection of a beta-receptor antagonist-propranolol, but was not blocked by the icv injection of an alpha1 -or (alpha2 -receptor antagonist prazosin or yohimbine. Icv injected naloxone but not ith injected naloxone blocked or reversed the EA-DpB. Results suggest that central P-receptors or opioid receptors in the brain are selectively involved in the EA-DpB.

Role of adrenoceptors in vasopressin, oxytocin and prolactin responses to conditioned fear stimuli in the rat

Conditioned fear or novel environmental stimuli suppress vasopressin (VP) and augment oxytocin (OT) and prolactin (PRL) release in rats. We examined the effects of intracerebroventricular (i.c.v.) injections of adrenoceptor antagonists on these neuroendocrine responses to conditioned fear or novel environmental stimuli in male rats. A beta1 antagonist, metoprolol, blocked the VP but not the OT or PRL response to conditioned fear stimuli, but did not abolish neuroendocrine responses to novel environmental stimuli. A beta2 antagonist, ICI118551, impaired the PRL but not the VP or OT response to fear or novel environmental stimuli. In rats injected with a alpha1 adrenoceptor antagonist, benoxathian, conditioned fear stimuli did not significantly induce the VP, OT or PRL responses. The effects of benoxathian were not due to a general reduction of arousal, since benoxathian did not prevent the VP, OT or PRL response to novel environmental stimuli. These data suggest that beta1 adrenoceptors play a selective role in the VP response to conditioned fear stimuli, as do beta2 adrenoceptors in the prolactin response to conditioned fear and novel environmental stimuli. We conclude that alpha1 adrenoceptors play a facilitative role in VP, OT, PRL responses to conditioned fear stimuli.

Effects of suramin on neuroendocrine and behavioural responses to conditioned fear stimuli

Conditioned fear stimuli suppress motor activity. The fear stimuli suppress vasopressin and facilitate oxytocin and prolactin release. These fear responses are impaired by selective destruction of noradrenergic neurones. Adenosine 5'-triphosphate is co-released from noradrenergic nerve terminals with noradrenaline. Thus the possibility arises that the behavioural and neuroendocrine responses may be mediated by purinergic rather than noradrenergic synapses. We examined whether suramin, an inhibitor of P2 and NMDA receptors, blocks conditioned fear responses. Suramin injected i.c.v. 30 min before testing stimuli impaired conditioned fear responses. The role of purinergic P2 receptors in expression of the behavioural and neuroendocrine responses to conditioned fear stimuli is discussed.

[Roles of vagal projection areas afferents on vagal input-evoked depressor response]

Vagal afferents project directly or indirectly to several brain areas. In urethane-anesthetized and bilaterally vagotomized rats, either procaine injection into the nucleus tractus solitarii (NTS) or beta-endorphin antiserum injection into the rostral ventrolateral medulla (RVL) markedly decreased the depressor (DpV) and bradycardia response to stimulation of cervical vagal afferents, while propranolol (or beta-endorphin antiserum) injection into the nucleus paraventricularis and procaine injection into the area postrema had no significant effect. In left vagotomized rats, the DpV remained unchanged after methyl atropine (i.v), but the bradycardia response during the DpV was attenuated. Since our previous study has shown the NTS can induce a depressor response via its beta-endorphinergic projections to RVL, the above results suggest that the inhibitory effect of vagal afferents on the RVL-sympathoexcitatory neurons via NTS beta-endorphinergic neurons represents one aspect of the mechanism underlying DpV.

Beta-endorphinergic neurons in nucleus arcuatus and nucleus tractus solitarii mediated depressor-bradycardia effect of "Tinggong" 2Hz-electroacupuncture

The central neural mechanisms underlying the depressor-bradycardia effect of the "Tinggong" 2Hz-electroacupuncture (EA-DpB) were analyzed: (1) Brain transection caudal to nucleus arcuatus (AR) or procaine preinjection into bilateral AR could block the EA-DpB; (2) preinjection of naloxone into bilateral nucleus paraventricularis could even reverse the EA-DpB, but beta-endorphin antiserum had no significant effect on the EA-DpB; (3) after procaine injection into the nucleus commissuraris (the caudal part of NTS), the EA-DpB was also blocked; (4) preinjection of naloxone or beta-endorphin antiserum into bilateral rostral ventrolateral medulla (RVL) attenuated or reversed the EA-DpB response, taken together with our previous findings that the RVL mediates the depressor response to the excitation of the beta-endorphinergic neurons in AR or NTS, the above results suggest that the EA-DpB is mediated by the beta-endorphinergic projections from the AR and NTS to RVL. Finally the mechanism underlying the reverse of the EA-DpB by naloxone injection into nucleus paraventricularis was discussed.

Tinggong(SI 19), a novel acupoint for 2Hz electroacupuncture-induced depressor response

In urethane-anesthetized, tubocurarine-immobilized and artificially ventilated rats, the specific electroacupuncture (EA, 2 Hz, 3 V) being delivered to bilateral "Tinggong (SI 19)-Quchi (LI 11)" induced a depressor response, while 10 Hz-EA, and 2 Hz-EA to either non-acupoints, "Hegu (LI 4)-Quchi" or "Taichong (Liv 3)-Quchi" did not. Pretreatment of either phentolamine, Propranolol or methyl atropine (i.v.) could markedly reduce the depressor response, indicating that the sympathetic vasoconstrictor nerve, the cardia sympathetic nerve and cardiac vagal nerve all are involved in the hypotensive response.