Where wild minds come to rest
Hm. I've never heard of this before and I'm quite an avid reader of crazy supplements and vitamins & minerals. In the case of herbal remedies (few work, many of quackery!) Wiki will honestly be about the most reliable source, however odd that is to say! And it says this:
The European species did not enter into the herbalists' pharmacopeia. In the American Old West the Western white clematis, Clematis ligusticifolia, was called pepper vine by early travelers and pioneers of the American Old West, who took a tip from Spanish colonials and used seeds and the acrid leaves of yerba de chivato as a pepper substitute. The entire genus containsessential oils and compounds which are extremely irritating to the skin and mucous membranes. Unlike black pepper or Capsicum, however, the compounds in clematis cause internal bleeding of the digestive tract if ingested in large amounts. C. ligusticifolia is essentially toxic. When pruning them, it's a good idea to wear gloves. Despite its toxicity, Native Americans used very small amounts of clematis as an effective treatment for migraine headaches and nervous disorders. It was also used as an effective treatment of skin infections. Clematis is also a constituent ofBach's Rescue Remedy. Leaf extracts from two Ethiopian species (Clematis longicauda steud ex A. Rich. and Clematis burgensis Engl.) are used locally to treat ear disorders and eczema. Phytochemical screening of the extracts from both of these species showed antibacterial and antifungal activity. The Extracts of these plants also posses wound healing and anti-inflammatory activities which could also be attributed to the phytoconstituents. 
Clematis has been listed as one of the 38 plants that are used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
So it certainly has effects on the brain being used for headaches however it can be lethal. (It comes from buttercups! Which as a kid I knew not to eat because they could make me sick.) So most likely the supplement version may not be lethal (how could they sell it!) I wouldn't think it would do wonders. =(
Hey, definitely keep us posted for ANY effects that it does cause. Sometimes strangely enough those herbal things do cause strange things. I recently read in the FB group someone posting success in using Brahmi herb (Ayurvedac medicine) for daydreaming and other 'brain' things. It wasn't very expensive and the other things it is believed to help are trouble areas, so it wasn't a big investment. (But I won't commit to posting much until I try it and see what comes of it.) It's amazing what some strange natural things CAN do, however limited.