This invention relates to indolylalkylamine metabolites as 5-hydroxytryptamine-6 ligands This invention relates to indolylalkylamine metabolites as 5-hydroxytryplamine-6 ligands^ to pharmaceutical compositions containing them, to methods of treatment using them, and to methods of determining the metabolism of (1-ary!sulfonyl-1 H-indol-3-yl)ethylamine derivatives using them. BACKGROUND OF THE INVENTION Various central nervous system disorders such as anxiety, depression, motor disorders, etc., are believed to involve a disturbance of the neurotransmitter 5-hydroxytryptamine (5-HT) or serotonin. Serotonin is localized in the central and peripheral nervous systems and is known to affect many types of conditions including psychiatric disorders, motor activity, feeding behavior, sexuai activity, and neuroendocrine regulation among others. The effects of serotonin are regulated by the various 5-HT receptor subtypes. Known 5-HT receptors include the 5-HT1 family (e.g. 5-HT1A), the 5-HT2 family (e.g. 5-HT2A), 5-HT3, 5-HT4, 5-HT5, 5-HT6 and 5-HT7 subtypes. The human 5-hydroxytryptamine-6 (5-HT6) receptor subtype has been cloned, and the extensive distribution of its mRNA has been reported. Highest levels of 5-HT6 receptor mRNA have been observed in the olfactory tubercle, the striatum, nucleus accumbens, dentate gyrus and CA1, CA2 and CAS regions of the hippocampus. Lower levels of 5-HT6 receptor mRNA are seen in the granular layer of the cerebellum, several diencephalic nuclei, amygdala and in the cortex. Northern blots have revealed that 5-HT6 receptor mRNA appears to be exclusively present in the brain, with little evidence for its presence in peripheral tissues. The high affinity of a number of antipsychotic agents for the 5-HT6 receptor, in addition to its mRNA localization in striatum, olfactory tubercle and nucleus accumbens suggests that some of the clinical actions of these compounds may be mediated through this receptor. Therefore, 5-HT6 receptor ligands are believed to be of potential use in the treatment of certain CNS disorders such as anxiety, depression, epilepsy, obsessive compulsive disorder, attention deficit disorder, migraine, cognitive memory enhancement (e.g. for the treatment of Alzheimer''s disease), sleep disorders, feeding disorders (e.g. anorexia or bulimia), neurodegenerath/e disorders (e.g. stroke or head trauma), panic attacks, withdrawal from drug abuse (e.g. cocaine, ethanol, nicotine or benzodiazepines), schizophrenia, or the like; or in the treatment of certain gastrointestinal disorders such as irritable bowel syndrome. Indolylalkylamine derivatives such as those described in patent application publication US2003-0171353A-1 are potent and selective 5-HT6 ligands. Until now, metabolites of said indolylalkylamine derivatives have not been identified, isolated, purified or synthesized. Therefore, it is an object of this invention to provide compounds which are metabolites of indolylalkylamine 5-HT6 ligands and which are useful as therapeutic agents in the treatment of a van''ety of central nervous system disorders related to or affected by the 5-HT6 receptor. It is another object of this invention to provide therapeutic methods and pharmaceutical compositions useful for the treatment of central nervous system disorders that are alleviated by 5-HT6 ligands. It is a further object of this invention to provide a method to determine the metabolism of an indolylalkylamine derivative. These and other objects and features of the invention will become more apparent by the detailed description set forth hereinbelow. SUMMARY OF THE INVENTION (I) The present invention provides a compound of (Formula Remove) /herein Q is C02RS or CH2NRGCOR7; r! is H or CrC6alkyl; R2 is an aryl or heleroaryl group each optionally substituted or an optionally substituted 8- to 13-membered bicyclic or tricyclic ring system having a N atom at the bridgehead and optionally containing 1, 2 or 3 additional heteroatoms selected from N, O or S; R3 and R* are each independently H, halogen, CN, OCO2R8, CO2R9| CONR,,^,, CNR12NR13RM, SOmR15l NR,BR17, OR1B, COR19 or a Cr C6alkyl, CrC6alkenyl, C2-C6alkynyl, CrCecycloalkyl, cycloheteroalkyl, ary! or heteroaryl group each optionally substituted; R5 and R6 are each independently H or Ct-Csalkyl; HO yOH R7 is Ci-Cea''ky'' or -o\ v-oh ; o~CO2H m is 0 or an integer of 1 or 2; rb, Rg, ris and R18 are each independently H or a CrC6alkyl, C2-C6alkenyl, C2-C6alkynyl, C3-C6cycloalkyl, cycloheteroalkyl, aryl or heteroaryl group each optionally substituted; R10, Rn and R18 are each independently H or a C-i-Cealkyl, aryl or heteroaryl group each optionally substituted; or R10 and R,, may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; and R«, ris, R«, rib and R17 are each independently H or a CrC4alkyl, aryl or heteroaryl group each optionally substituted; or Ri3 and R14 or R1€ and R17 may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; or a stereoisomer thereof or a pharmaceuticatly acceptable salt thereof. The present invention also provides methods and compositions useful for the therapeutic treatment of central nervous system disorders related to or affected by the 5-HT6 receptor and a method to determine the metabolism of an indolylafkylamine derivative. DETAILED DESCRIPTION OF THE INVENTION The ability of the 5-hydroxytryptamine-6 (5-HT6) receptor to bind a wide range of therapeutic compounds used in psychiatry, coupled with its intriguing distribution in the brain has stimulated significant interest in new compounds whic are capable of interacting with or affecting said receptor. Significant efforts are being made to understand the possible role of the 5-HTG receptor in psychiatry, cognitive dysfunction, motor function and control, memory, mood and the like. To that end, compounds which demonstrate a binding affinity for the 5-HT6 receptor are earnestly sought as potential therapeutic agents in the treatment of central nervous system disorders, for example see C. ReaviH and D. C. Rogers, Current Opinion in Investigational Drugs, 2001, 2(1):104-109, Pharma Press Ltd. Indolylaikylamine derivatives having a potent and selective binding affinity for the 5-HT6 receptor and their preparation are described in patent application publication US2003-0171353A-1, incorporated herein by reference thereto. Until now, metabolites of said indolylalkylamine derivatives have not been identified, isolated, purified or synthesized. Surprisingly, if has now been found that compounds of formula I are metabolites of indolyiaikyiamine 5-HT6 derivatives. Advantageously, said formula I compounds may be used as effective therapeutic agents for the treatment of central nervous system (CN5) disorders associated with or affected by the 5-HT6 receptor Accordingly, the present invention provides a compound of formula I R2 is an aryl or heteroaryl group each optionally substituted or an optionally substituted 8- to 13-membered bicyclic or tricyclic ring system having a N atom at the bridgehead and optionally containing 1, 2 or 3 additional heteroatoms selected from N, O or S; R3 and Rt are each independently H, halogen, CN, OCOZR8, CO2R9, CONR10Rn, CNR12NR,3Ri4, SOmR15, NR16R,r, OR18, COR19 or a C,-Cea!kyl( C2-C6alkenyl. C2-C6alkynv|, C3-C6cycloalkyl, cycloheteroalkyl, aryl or heteroaryl group each optionally substituted; R5 and R6are each independently H or d-C6alkyl; ho yOH R7 is Cj-Csalkyl or -o-( v-oh ; o-< CO2H m is 0 or an integer of 1 or 2; Ra, rs, Rts and R18 are each independently H or a CrC6alkyl, C2-Cflalkenyl. C2-C6alkynyl, C3-Cecycloalkyl, cycloheteroalkyl, aryl or heteroaryl group each optionally substituted; R,o, Rn and R1B are each independently H or a d-C6alkyl, aryJ or heteroaryl group each optionally substituted; or R10 and rh may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; and Riz. ris, rm, R« and R^ are each independently H or a C,-C4alkyl, aryl or heteroaryl group each optionally substituted; or R13 and RH or R16 and R,7 may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; or a stereoisomer thereof or a pharmaceutically acceptable salt thereof. As used in the specification and claims, the term halogen designates Br, Cl, ! or F. The term cycloheteroalkyl designates a five- to seven-membered cycloalkyl ring system containing 1 or 2 heteroatoms, which may be the same or different, selected from N, O or S and optionally containing one double bond. Exemplary of the cycloheteroalkyl ring systems included in the term as designated herein are the following rings wherein X is NR, O or S; and R is H or an optional substituent as described hereinbelow: R Similarly, as used in the specification and claims, the term heteroaryl designates a five- to ten-membered aromatic ring system containing 1, 2 or 3 heteroatoms, which may be the same or different, selected from N, O or S. Such heteroaryl ring systems include pyrrolyl, azolyl, oxazolyl, thiazolyl, imidazolyl, furyl, thienyl, quinolinyl, isoquinolinyl, indolyl, benzothienyl, benzofuranyl, benzisoxazolyl or the like. The term aryl designates a carbocyclic aromatic ring system e.g. of 6-14 carbon atoms, such as phenyl, naphthyl, anthracenyl or the like. The term haloalkyl as used herein designates a CnH^+i group having from one to 2n+1 halogen atoms which may be the same or different and the term haloalkoxy as used herein designates an OCnH2n*i group having from one to 2n+1 halogen atoms which may be the same or different. Exemplary of the 8- to 13-membered bicyclic or tricyclic ring systems having a N atom at a bridgehead and optionally containing 1, 2 or 3 additional heteroatoms selected from N, O or S included in the term as designated herein are the following ring systems wherein W is NR, O or S; and R is H or an optional substituent as described hereinbelow: (Formula Remove) In the specification and claims, when the terms l, C2-C6alkenyl, CrC6alkynyl, C3-C7cycloalkyl, cycloheteroalkyl, aryl. heteroaryl or 8- to 13-membered bicyclic or tricyclic ring system having a N atom at the bridgehead are designated as being optionally substituted, the substituent groups which are optionally present may be one or more, e.g. two or three, the same or different of those customarily employed in the development of pharmaceutical compounds or the modification of such compounds to influence their structure/activity, persistence, absorption, stability or other beneficial property. Specific examples of such substituents include halogen atoms, nitro, cyano, thiocyanato, cyanato, hydroxyl, alkyl, haloalkyl, alkoxy, haloalkoxy, amino, alkylamino, dialkylamino, formyl, alkoxycarbonyl, carboxyl, alkanoyl, alkylthio, alkylsuphinyl, alkylsulphonyl, carbamoyl, alkylamido, phenyl, phenoxy, benzyl, benzyloxy, heteroaryl, cycloheteroalkyl or cycloalkyl groups, preferably halogen atoms or CrCealkyl groups. Typically, 0-3 substituents, the same or different, may be present. When any of (he foregoing substituents represents or contains an alkyl substituent group e.g. aikoxy, alkanoyl, this may be linear or branched and may contain up to 12, preferably up to 6, more preferably up to 4 carbon atoms. Pharmaceutically acceptable salts may be any acid addition salt formed by a compound of formula I and a pharmaceutically acceptable acid such as phosphoric, sulfuric, hydrochloric, hydrobromic, citric, maleic, malontc, mandelic. succinic, fumaric, acetic, lactic, nitric, sulfonic, p-toluene sulfonic, methane sulfonic acid or the like. Compounds of the invention include amides, esters, carbamates or other conventional prodrug forms, which in general, are functional derivatives of the compounds of the invention and which are readily converted to the inventive active moiety in v/Vo. Correspondingly, the method of the invention embraces the treatment of the various conditions described hereinabove with a compound of formula I or with a compound which is not specifically disclosed but which, upon administration, converts to a compound of formula I in vivo. Also included are metabolites of the compounds of the present invention defined as active species produced upon introduction of these compounds into a biological system. When a compound of formula I contains one or more chiral centers or asymmetric carbons, then said formula I compound may exist as one or more stereoisomers. The various stereoisomers include enantiomers, diastereomers, atropisomers and geometric isomers. One skilled in the art will appreciate that one stereoisomer may be more active or may exhibit beneficial effects when enriched relative to the other stereoisomer(s) or when separated from the other stereoisomer(s). Additionally, the skilled artisan knows how to separate, enrich or selectively prepare said stereoisomers. Accordingly, the present invention comprises compounds of Formula I, the stereoisomers thereof and the pharmaceutically acceptable salts thereof. The compounds of the invention may be present as a mixture of stereoisomers, individual stereoisomers, or as an optically active form. Preferred compounds of the invention are those compounds of formula I wherein ri, R3 and R« are H. Also preferred are those compounds of formula I wherein R2 is an imidazolyl or imidazothiazolyl group each optionally substituted. Another group of preferred compounds of formula I are those compounds wherein Q is CO2H, CH2NHCOCH3 orCH2NHCO2 CO2H More preferred compounds of the invention are those compounds of formula I wherein R1t R3 and R, are H and R2 is an imidazolyl or imidazothiazolyl group each optionally substituted. Another group of more preferred compounds are those compounds of formula I wherein R1§ R3and R< are H; R2 is an imidazolyl or imidazothiazolyl group each optionally substituted; and Q is HO /Oh CH2NHCOCH3 or CH2NHC02-\ voh . CO2H Among the preferred compounds of the invention are: N-(2-{1-[(6-chloroimidazo[2,1 -b][1,3]thiazol-5-yl)sulfony!]-1 H-indol-3- yl}ethyl)acetamide; 1-O-{[(2-{1-[(6-chloroimidazo[2,1-b][1,3lthiazol-5-yl)sulfonyl]-1H-indol-3- yl}ethyl)amino]carbonyl}-beta-D-gIucopyranuronicacid; {1 -[(6-chloroimidazo[2,1 -b][1,3]thiazol-5-yl)sulfonyl]-1 H-indol-3-yl}acetic acid; N-[(1 -{[4-chtoro-2-(methylthio)-1 H-imidazol-5-yl)sulfonyl}-1 H-indol-3-yl)methyl]acetamide; a stereoisomer thereof; or a pharmaceutically acceptable salt thereof. Compounds of me invention may be conveniently prepared using conventional synthetic methods and, if required, standard separation and isolation techniques. For example, compounds of formula I wherein Q is CO2R5 (la) may be prepared by sequentially reacting an indole derivative of formula II with a strong base, such as n-butyllithium, KOt-Bu or NaH, and an arylsulfonyl hatide, The reaction is shown in flow diagram I. Flow Diagram I C02R5 1a) base 1b) CISO2R2 (Formula Remove) (ID (la) Compounds of formula I wherein Q is CHzNRsCOR? and R7 is CVCealkyl (lb) may be prepared by reacting a compound of formula HI with an anhydride of formula IV in the presence of a base, such as N(C2H5)3 and optionally in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP). The reaction is shown in flow diagram II. Flow Diagram II (Formula Remove) SO2R2 S02R2 (CrC6alkylCO)2O (IV) N(C2H5)3 DMAP NHCOCrC6alkyl (111) (lb) Compounds of formula I wherein Q is O-glucopyranuronic acid (Ic) may be prepared by reacting the compound of formula lit with di-t-butyldicarbonate [ 200eC), identified by mass spectral and NMR analyses. EXAMPLE 3 Preparation of 3. 4. 5-TriacetoxY-6-(2-{1-f(6-chloroimidazor2.1-bin.31thiazol-5-yl)sulfonvl]-1H-indol-3-vl)ethvcarbamoYloxv)tetrahvdropvran-2-carboxvlicacid methyl ester (Formula Remove) A solution of (Boc)2O (1.8 g, 8.3 mmol, 1.2 eq) in CH3CN is cooled to 0 °C (ice-water bath), treated dropwise with DMAP (203 mg, 1.66 mmol, 0.2 eq) in CH3CN, stirred for 5 min, treated dropwise with 2-{1-[(6-chIoroimidazo[2,1-b][1,3]thiazol-5-yl)sulfonyl]-1H-indol-3-yl}ethylamine (2.6 g, 6.9 mmol) in CH3CN, stirred for 30 min (isocyanate is generated in situ) at 0°C, concentrated using rotavapor to remove the CH3CN and chased with toluene. The resultant residue is dissolved in toluene, treated dropwise with a solution of hydroxyglucuronic ester (2.6 g, 7.7 mmol, 1.1 eq) in toluene followed by triethylamine (1.2 mL), stirred for 2h at 0 °C, allowed to warm to room temperature, stirred for 16h and concentrated to dryness. This residue is purified by column chromatography (20-50 % THF in heptane as eluent) to afford the pure /?-anorner of the title product, 2 g (39 % yield) and a mixture of o and /?-anomers (1:1.6), 2.5 g (49 % yield). The anomers are identified by NMR analysis. 1H NMR (300 MHz, CDCI3): /?-anomer4: 8.01 (d, 1H, J = 4.5 Hz), 7.95-7.91 (m, 1H), 7.53-7.50 (m, 1H), 7.45 (s, 1H), 7.35-7.26 (2H, m), 7.17 (d, 1H, J = 4.5 Hz), 5.74 (d, 1H, J = 8.1 Hz), 5.36-5.09 (m, 3H), 4.99 (1H, m), 4.19 (d, 1H, J - 9.9 Hz), 3.75 (s, 3H), 3.57-3.41 (2H, m), 2.92 (2H, t. J= 7.0 Hz), 2.04, 2.03, 2,02 (3s, 9H). MS [M+Hf = 741. a-anomer (200 mg. contains 2% /?-anomer) 1H NMR MHz CDCI,): 8.03 (d. 1H, J = 4.2 Hz), 7.94-7.91 (m, 1H), 7.56-7.53 (m, 1H), (s, 1H), 7.35-7.26 (2H, m), 7.14 (d, 1H, J = 4.8 Hz), 6.33 (d, 1H, J- 3.6 Hz), 5.52-5.46 (m, 1H), 5.26-5.10 (3H, m), 4.38 (d, 1H, J= 10.2 Hz), 3.74 (s, 3H), 3.57- (2H, m), 2.92 (2H, t, J = 7.0 Hz), 2.03 (3s, 9H). EXAMPLE 4 Preparation of 1-O-{f(2-f1-n6-Chloroimidazor2.1-b]ri.3lthiazol-5-vl)sulfonvn-1H-indol-3-vl)ethvl)amino1carbonvl}-beta-D-qlucopyranuronicacid (Formula Remove) 6-chloroimidazo[2,1-b][1,3]thiazol-5-yl)suifonyl]-1 H-indol-3-yl}ethycarbamoyloxy)tetrahydropyran-2-carboxylic acid methyl ester (1.0 g, 1.35 mmol) in THF is treated with CH3OH (38.8 ml) and H2O (10 ml), cooled to 0 °C (ice-water bath), treated with a solution of LiOH »H2O (340 mg, 8.1 mmol, 6 eq) in H20 (5.5 ml) [0.1 N LiOH/MeOH/THF/H2O] and stirred at 0 °C for 2 h under N2 atmosphere. Progress of the deprotection is monitored via reversed-phase TLC (SiO2-C18 MeCN/H2O, 3/7). The reaction mixture is diluted with 150 mL of H2O, neutralized by the addition of 10 g of amberlite-120 (plus) cation exchange material (H+ form) and filtered. The filtrate is concentrated under reduced pressure to an aqueous suspension. This suspension is freeze dried and lyophilized to give the title product, 700 mg (86% yield). Further purification by silica gel column chromatography [CHCI3/CH3OH/H2O (7:3:0.5) as a eluent] provides the title product, 310 mg, 98% pure, identified by mass spectral and NMR analyses. 1H NMR (300 MHz, DMSO-de): 8.31 (d, 1H, J = 4.5 Hz), 7.94-7.91 (m, 1H), 7.82 (s, 1H), 7.69 (d, 1H, J = 4.2 Hz), 7.64-7.57 (m, 2H), 7.39-7.27 (m, 2H), 5.31 (d, 1H, J = 8.1 Hz), 3.69 (d, 1H. J = 9.0 Hz), 3.37-3.13 (m, 5H), 2.82 (t, 2H, J = 7.0 Hz); 13C (75 MHz, DMSO-d6): 170.6, 155.4, 155.3, 152.3, 139.2, 134.9, 131.6, 125.7. 124.5, 124.4, 121.1, i^i.i, uu./. 118.8, 116.6, 113.8, 95.5, 76.6. 76.5, 72.8, 72.0, 25.2; LC/MS (ESI) retention time = 35.12, [M+H]* = 600.7. The a-anomer (57 mg) is obtained in the same manner described above, identified by HPLC and mass spectral analyses. LC/MS (ESI) retention time = 27.11 min, [M+H]* = 600.8. EXAMPLE 5 Comparative Evaluation of S-HT6 Binding Affinity of Test Compounds The affinity of test compounds for the serotonin 5-HT6 receptor is evaluated in the following manner. Cultured Hela cells expressing human cloned 5-HT6 receptors are harvested and centrifuged at low speed (1,000 x g) for 10.0 min to remove the culture media. The harvested cells are suspended in half volume of fresh physiological phosphate buffered saline solution and recentrifuged at the same speed. This operation is repeated. The collected cells are then homogenized in ten volumes of 50 mM Tris.HCI (pH 7.4) and 0.5 mM EDTA. The homogenate is centrifuged at 40,000 x g for 30.0 mm and the precipitate is collected. The obtained pellet is resuspended in 10 volumes of Tris.HCI buffer and recentrifuged at the same speed. The final pellet is suspended in a small volume of Tris.HCI buffer and the tissue protein content is determined in aliquots of 10-25 pi volumes. Bovine Serum Albumin is used as the standard in the protein determination according to the method described in Lowry et al., J. Biol. Chem.. 193:265 (1951). The volume of the suspended cell membranes is adjusted to give a tissue protein concentration of 1.0 mg/ml of suspension. The prepared membrane suspension (10 times concentrated) is aliquoted in 1.0 ml volumes and stored at -70° C until used in subsequent binding experiments. Binding experiments are performed in a 96 well microtiter plate format, in a total volume of 200 pi. To each well is added the following mixture: 80.0 ul of incubation buffer made in 50 mM Tris.HCI buffer (pH 7.4) containing 10.0 mM MgCI2 and 0.5 mM EDTA and 20 pi of [3H]-LSD (S.A., 86.0 Ci/mmol, available from Amersham Life Science), 3.0 nM. The dissociation constant, K0 of the [3H]LSD at the human serotonin 5-HT6 receptor is 2.9 nM, as determined by saturation binding with increasing concentrations of {3H]LSD. The reaction is initiated by the final addition of 100.0 |jl of tissue suspension. Nonspecific binding is measured in the presence of 10.0 uM methiothepin. The test compounds are added in 20.0 ul volume. The reaction is allowed to proceed in the dark for 120 m in at room temperature, at which time, the bound ligand-receptor complex is filtered off on a 96 well unifilter with a Packard Filtermate® 196 Harvester. The bound complex caught on the Her disk is allowed to air dry and the radioactivity is measured in a Packard TopCount® equipped with six photomultiplier detectors, after the addition of 40.0ul Microscint®-20 scintillant to each shallow well. The unifilter plate is heat-sealed and counted in a PackardTopCount® with a tritium efficiency of 31.0%. Specific binding to the 5-HT6 receptor is defined as the total radioactivity bound less the amount bound in the presence of 10.0uM uniabeled methiothepin. Binding in the presence of varying concentrations of test compound is expressed as a percentage of specific binding in the absence of test compound. The results are plotted as log % bound versus log concentration of test compound. Nonlinear regression analysis of data points with a computer assisted program Prism® yielded both the IC50 and the K| values of test compounds with 95% confidence limits. A linear regression line of data points is plotted, from which the IC50 value is determined and the ki value is determined based upon the following equation: K, = IC50 / (1 + L/KD) where L is the concentration of the radioactive ligand used and kd is the dissociation constant of the ligand for the receptor, both expressed in nM. Using this assay, the following Ki values are determined and compared to those values obtained by representative compounds known to demonstrate binding to the 5-HT6 receptor. The data are shown in Table I, below. Table I Test Compound 5-HT6 Binding Ki (Ex. No.) (nM) 1 26 2 248 4 5-HT6 Binding Ki Comparative Examples Clozapine 6.0 Loxapine 41 .4 Bromocriptine 23.0 Methiothepin 8.3 Mianserin 44.2 Olanzepine 19.5 As can be seen from the results set forth above, the compounds of the present invention demonstrate significant affinity for the 5-HT6 receptor. What is claimed is: 1. A compound of (Formula Remove) wherein Q is CO2RS or CH2NR6COR7; R) is H or CrC6alky!; R2 is an aryl or heteroaryl group each optionally substituted or an optionally substituted 8- to 13-membered bicyclic ortricyclfc ring system having a N atom at the bridgehead and optionally containing 1, 2 or 3 additional heteroatoms selected from N, O or S; R3 and R, are each independently H, halogen, CM, OCO2RB, CO2R9, CONR10Rii, CNR12NR13R,4, SOmR15l NR16Ri7, OR18, COR19 or a Cr C6alkyl, CrCsalkenyl, C2-C6alkynyl, C3-C6cycloalkyl, cycloheteroalkyl, aryl or heteroaryl group each optionally substituted; R5 and rs are each independently H or d-Cealkyl; HO /OH R7 is CrC6alkyl or -o\ v-oh ; p-< CO2H m is 0 or an integer of 1 or 2; Rs, R», ris and R« are each independently H or a CrC6alkyl, C2-C6alkenyl, Ca-Cealkynyl, C3-C6cycloalkyl, cycloheteroalkyl, aryl or heteroaryi group each optionally substituted; rio, Rn and R16 are each independently H or a Ci-CBalkyl, aryl or heteroaryl group each optionally substituted or R10 and R^ may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; and Ria, R«, rh, R« and R17 are each independently H or a d-dalkyl, aryl or heteroaryl group each optionally substituted; or R13 and R14 or R16 and R17 may be taken together with the atom to which they are attached to form a 5- to 7-membered ring optionally containing another heteroatom selected from O, N or S; or a stereoisomer thereof or a pharmaceutically acceptable salt thereof. The compound according to daim 1 wherein Ri, R3 and R4 are H. The compound according to claim 1 or claim 2 wherein R2 is an imidazolyl or imidazothiazolyl group each optionally substituted. A. The compound according to any one of claims 1 to 3 wherein Q is 5. The compound according to claim 1 selected from the group consisting of: N-(2-{1-[(6-chloroimidazo[2,1-b][1,3]thiazol-5-yl)sulfonyl]-1H-indol-3- yl)ethyl)acetamide; yl}ethyl)amino]carbonyl}-beta-D-g!ucopyranuronicacid; {1-[(6-chloroimidazo[2,1-b][1,3]thiazo!-5-yl)sulfonyl]-1H-indol-3-yl}aceticacid; N_[(1 -{[4-chloro-2-(methylthio)-1 W-imidazo!-5-yl]su!fanyl}-1 H-indol-3- yl)methyl]acetarnide; a stereoisomer thereof; and a pharmaceutically acceptable salt thereof. The compound according to claim 5 which is N-(2-{1-[(6- chloroimidazo[2,1-b][1,3]thiazol-5-yl)sulfonyl]-1H-indol-3-y!}ethyl)acetamide. The compound according to claim 5 which is 1-O-{[(2-{1-[(6- chloroimidazo[2,1-b][1,3]thiazol-5-yl)sulfonyl]-1H-indol-3-yl}ethyl)amino]carbonyl}- beta-D-glucopyranuronic acid. A method for the treatment of a disorder of the central nervous system related to or affected by the 5-HT6 receptor in a patient in need thereof which comprises providing to said patient a therapeutically effective amount of a compound of formula I according to any one of claims 1 to 7. The method according to claim 8 wherein said disorder is selected from the group consisting of a neurodegenerative disorder; an anxiety disorder; and a cognitive disorder. The method according to claim 9 wherein said anxiety or cognitive disorder is selected from the group consisting of attention deficit disorder; obsessive compulsive disorder; and general anxiety disorder. A pharmaceutical composition which comprises a pharmaceutically acceptable carrier and an effective amount of a compound of formula I according to any one of claims 1 to 7. A method for the determination of the metabolism of a (1-arylsulfonyl- 1H-indol-3-yl)ethylamine derivative which comprises evaluating a test sample for the presence of a compound of formula I according to any one of claims 1 to 7. 13. The use of a compound according to any one of claims 1 to 7 in the manufacture of a medicament for the treatment of a neurodegenerative disorder, an anxiety disorder or a cognitive disorder. Applicant''s Agent 14. An Invention substantially such as herein before described.